TREATISE  ON 
APPLIED  ANALYTICAL  CHEMISTRY 


TREATISE    ON 

APPLIED  ANALYTICAL 

CHEMISTRY 

METHODS    AND    STANDARDS 

for    the   Chemical    Analysis   of   the    principal 
Industrial  and  Food   Products 

By 

PROFESSOR    VITTORIO    VILLAVECCHIA 

Director  of  the  Chemical  Laboratories  of  the   Italian  Customs 

WITH    THE    COLLABORATION    OF 

G.  FABRIS  A.  BIANCHI  G.  ARMANI 

G.  ROSSI  G.  SILVESTRI  G.  BOSCO 

R.  BELASIO  F.  BARBONI  A.  CAPPELLI 

TRANSLATED    BY 

THOMAS  H.  POPE,  B.Sc.,  A.C.G.I.,  F.I.C. 

University  of  Birmingham 


VOL.  I. 

WITH    58    ILLUSTRATIONS    IN    THE    TEXT 


PHILADELPHIA 

P.  BLAKISTON'S  SON  &  CO. 

10 1 2    WALNUT    STREET 
1918 


(vf 


Printed  in  Great  Britain 


TRANSLATOR'S   NOTE 

In  the  preparation  of  the  present  translation,  the  points  on  which  it 
has  been  considered  desirable  to  depart  from  the  sense  of  the  Italian  text 
are  few  and  mostly  unimportant.  Notification  is  made  where  any  appre- 
ciable addition  to  or  modification  of  the  original  has  been  made  to  bring 
it  into  conformity  with  the  conditions  in  this  country. 

Temperatures  are  always  expressed  in  degrees  Centigrade,  and  concen- 
trations of  aqueous  alcohol  solutions,  according  to  the  French  custom,  in 
percentages  by  volume. 

THOMAS  H.  POPE. 
BIRMINGHAM. 


PREFACE 

Chemical  analysis  applied  to  the  examination  of  industrial  and  alimentary 
products  plays  an  important  part  in  the  purchase  of  raw  materials,  in  the 
control  of  manufacturing  processes,  and  in  the  determination  of  the  value, 
impurities  and  adulterations  of  the  finished  products.  It  constitutes,  in- 
deed, a  branch  of  chemistry  worthy  of  assiduous  cultivation  by  the  technical 
chemist  who  wishes  to  obtain  a  rational  knowledge  of  his  prime  materials 
and  finished  products,  by  the  hygienic  chemist  desirous  of  detecting  any 
additions  to  or  changes  in  food  substances,  by  the  commercial  chemist 
for  the  exact  characterization  and  evaluation  of  commercial  products, 
and,  in  general,  by  experts  and  inspectors  appointed  to  exact  contractual 
conditions  in  connexion  with  the  purchases  and  supplies  of  the  State. 

The  methods  followed  in  these  industrial  and  commercial  analyses  are 
applications  of  general,  analytical  and  physical  chemistry  to  special  cases  ; 
in  some  instances  they  are  less  rigorous  than,  and  do  not  attain  the  precision 
of,  scientific  methods,  whereas  in  others  the  accuracy  is  that  of  the  most 
exact  scientific  investigations.  The  choice  of  the  method  to  be  used  is  of 
considerable  importance  in  practice,  which  demands  processes  giving  the 
greatest  exactitude  compatible  with  the  end  in  view  at  the  lowest  possible 
expenditure  of  time  and  trouble. 

In  most  cases  numerous  methods  are  given  in  the  literature  for  the  ex- 
amination of  any  particular  material,  and  doubt  is  often  felt  as  to  which  of 
these  methods  it  is  preferable  to  employ,  the  more  so  since  the  differences 
frequently  lie  in  details  and  are  not  of  great  import.  Thus,  without  pre- 
liminary trial,  the  analyst,  especially  in  a  new  field,  cannot  always  decide 
easily  which  procedure  will  answer  his  purpose. 

It  may,  further,  be  pointed  out  that,  with  certain  products,  the  methods 
of  analysis  at  present  available  yield  results  which  are  not  absolute  but 
relative  only  to  the  procedure  employed.  In  such  cases  it  is  most  important 
that  different  workers  use  one  and  the  same  method — although  perhaps  not 
a  very  accurate  one — -in  order  that  the  results  obtained  may  exhibit  the 
necessary  concordance.  Then,  too,  certain  States  have  felt  the  necessity 
of  issuing  official  standards  to  be  attained  in  the  analysis  of  various  com- 
modities of  general  interest,  while  in  commercial  and  industrial  circles  the 
custom  is  growing  of  fixing  beforehand  the  analytical  methods  serving 
as  basis  for  the  evaluation  of  the  products  to  be  dealt  in. 

All  this  shows  how  useful  it  is  for  the  analyst  to  have  at  his  command 
a  collection  of  such  methods  and  standards  for  industrial  and  commercial 
analyses  as,  having  been  either  officially  prescribed  or  repeatedly  tested, 
may  be  confidently  adopted. 

To  this  end  the  results  obtained  over  a  long  period  in  the  Chemical 

vii 


viii  PREFACE 

Laboratories  of  the  Italian  Customs  Department  were  embodied  in  a  Manual 
of  Technological  Analytical  Chemistry,  which  was  published  in  1904  and  has 
been  out  of  print  for  some  years. 

With  a  similar  object  the  present  treatise  has  been  compiled.  Much 
still  remains  to  be  done,  and  the  methods  now  described  cannot  be  regarded 
as  final ;  in  the  present  state  of  knowledge  they  do,  however,  satisfy  prac- 
tical requirements  with  some  degree  of  sufficiency.  In  the  laboratories 
under  my  direction,  most  of  the  methods  have  been  repeatedly  tried  and 
many  of  them  carried  out  and  studied  almost  daily  by  specialists  who  are 
already  well  known  from  their  published  work  and  are  now  assisting  here 
with  their  valuable  co-operation.  To  these  and  also  to  those  colleagues 
and  friends  who  have  furnished  unpublished  analytical  data  and  particulars 
of  methods  based  on  their  practical  experience,  I  desire  to  express  my 
gratitude. 

This  treatise  is  divided  into  two  volumes.  The  first  deals  with  the 
analysis  of  potable  waters,  chemical  products,  fertilizers,  cement  materials, 
metals  and  alloys,  fuels,  tar  and  its  derivatives,  mineral  oils  and  fatty 
substances  and  the  industrial  products  derived  therefrom.  The  second 
treats  of  flesh  foods,  milk  products,  flour  and  starches,  sugars  and  saccharine 
products,  beer,  wine,  spirits  and  liqueurs,  essential  oils,  turpentine,  var- 
nishes, rubber,  tanning  materials,  leather,  colouring  matters,  and  textile 
fibres  and  fabrics. 

For  each  product  considered  a  brief  statement  is  first  made  of  the  different 
cases  and  the  analytical  problems  commonly  presenting  themselves,  as 
well  as  of  the  investigations  and  determinations  to  be  made  to  solve  them. 
Detailed  descriptions  are  then  given  of  the  methods  to  be  followed.  Some- 
times methods  for  groups  of  allied  substances,  to  which  they  are  applicable 
in  general,  are  collected  in  one  and  the  same  sub- chapter.  As  a  rule  but 
one  method  or  at  most  two  methods  are  given  for  each  separate  test  or 
determination  ;  when  it  is  deemed  necessary  to  give  a  greater  number,  the 
reason  for  this  is  stated,  and  the  cases  indicated  in  which  one  method  rather 
than  the  others  should  be  followed. 

In  some  instances  mention  is  made  of  details  to  be  observed  in  special 
cases  or  of  doubts  which  exist  as  to  the  accuracy  of  the  methods,  any  factors 
and  conditions  influencing  the  results  being  pointed  out.  Whether  the 
methods  have  been  adopted  by  official  or  other  bodies  is  also  stated. 

Next  are  given  criteria  and  standards,  with  the  aid  of  which  the  indus- 
trial, commercial  or  hygienic  value  of  the  product  may  be  ascertained  from 
the  analytical  data  obtained.  For  the  same  purpose  tables  are  given  con- 
taining examples  of  the  analytical  results  relating  to  the  ordinary  com- 
mercial qualities  of  the  product. 

It  is  my  hope  that  this  publication  may  be  received  cordially  by  Italian 
chemists,  to  whom  I  shall  be  grateful  for  suggestions  of  improvements  or 
additions. 

G.  VITTORIO  VILLA VECCHIA. 

ROME. 


CONTENTS 

PAGE 

CHAP.  I.— Waters        ... 

Potable  waters     .  .  • 

Partial  analysis 

Table  I.     Hardness  table        .  •  4 

IK  Complete  analysis 
Water  for  industrial  purposes 

Table  II.     Composition  of  water  supplies 

CHAP.  II. — Chemical   Products 

Acetone  ...  .  .          .          .        ID 

Acetone  oils          ...  .....        T7 

Acid,  Acetic          .          .          .          .          .          •          •          •          •          •      . 

Boric.          .  .  ....        19 

Carbonic     ...  ......        20 

Chromic      .          .  .  ...21 

Citric 

Lemon  juice   .....  ...        23 

Formic       ....  .....        25 

Hydrochloric       .          .          .          .          .          •          •          •          .26 

Hydrofluoric       .... 

Hydrofluobilicic  .... 

Lactic 

Nitric ....        29 

Oxalic •  -3° 

Phosphoric          .          .          .          .          .          .          •          •          •        31 

Picric          .......•••        32 

Sulphuric  .......•••       33 

Fuming  (Oleum)       .          .          .          .          •          -34 

Tartaric         ....  -35 

Tartar,  etc 36 

Alcohol,  Amyl  (Isoamyl)        .          .          .          .          .          •          •  3 8 

Ethyl .38 

Methyl    ....  38 

Table  III.     Specific  gravity  of  methyl  alcohol  solutions  .          .        40 
Alum  ...........       42 

Aluminium  acetate        .  42 

sulphate      .....  ...        43 

Ammonia     ......  ....        45 

Ammonium  carbonate  .  46 

chloride     .....  4^ 

persulphate         .....  47 

sulphate     .......  -47 

thiocyanate         ....  ...        47 

vanadate  .....  •        4$ 

Amyl  acetate        ......  -4* 

Aniline         ......  •          •        5° 

Aniline  oil  .....  •  51 

Toluidine.          .....  52 

ix 


CONTENTS 

PAGE 

Antimony  and  potassium  tartrate  ......        52 

Barium  chloride  ..........        53 

peroxide.  .........        53 

Baryta         .  54 

Bleaching  powder          .  .          .          .  .  ,  .          .  -55 

Borax  and  natural  borates  ........        56 

Bromine       .          .          .          .          .          .          .          .          .          .          .56 

Calcium  acetate  .          .  .          .          .          .          .          .          -57 

carbide  .........        58 

citrate     ..........        59 

Carbon  bisulphide          .........        62 

tetrachloride     .........        62 

Chloride  of  lime  ..........        63 

Chloroform  ..........        63 

Copper  sulphate  ..........        63 

Ether .          .          .65 

Ferric  chloride      ..........        65 

Ferrous  acetate    .          .  .......        66 

sulphate.          .          .          .          .          .          .          .          .          .66 

Formaldehyde       .......  67 

Hydrogen  peroxide        .          .          .          .          .          .          .          .          .68 

Hydrosulphites     ..........        69 

Iodine  ...........        70 

Lead  acetate         .          .          .          .          .          .          .          .          .          .71 

Magnesia      ...........        71 

Magnesium  chloride      ..........        73 

sulphate     .........        74 

Manganese  dioxide        .........  74 

Mercuric  chloride  .........  76 

Mercurous  chloride        .........  77 

Mordants,  Chrome         .........  77 

Iron     ..........  78 

Nitrobenzene         ..........  79 

Potassium  aluminium  sulphate      .          .          .          .          .          .          -79 

bisulphite     .........  79 

bitartrate     .........  80 

bromide       .........  80 

carbonate    .........  81 

chlorate        .........  82 

chloride        .........  83 

chromate      .........  83 

cyanide         .........  83 

dichromate  ........  84 

ferricyanide  ........  85 

ferrocyanide          ........  86 

hydroxide    .........  86 

iodide 88 

lactate 88 

nitrate          .........  89 

oxalate         .........  90 

permanganate       ........  90 

persulphate.          ........  91 

sulphate       .........  91 

sulphide       .........  91 

Silver  nitrate        ..........  92 

Sodium  acetate    ..........  92 


CONTENTS  xi 


PAGE 

Sodium  aluminate         ....... 

92 

bicarbonate      ........ 

93 

bisulphate         ........ 

94 

bisulphite          ....... 

94 

carbonate          ...... 

95 

chlorate  ...... 

.        98 

chloride  ........ 

99 

dichromate       ....... 

IOO 

hydroxide         ...... 

10  I 

nitrate     ......... 

10  I 

nitrite      .          .          .          .          .          .          ... 

101 

perborate          ........ 

IO2 

peroxide.          ........ 

IO2 

phosphate        ....... 

102 

silicate    ......... 

.        103 

stannate.          ........ 

104 

sulphate             ........ 

.        105 

sulphide            ........ 

106 

sulphite  ......... 

107 

thiosulphate     ........ 

.      108 

tungstate          ........ 

.      108 

Stannic  chloride  ......... 

.      108 

Stannous  chloride          ........ 

no 

no 

Sulphur  minerals       .          .          .          . 

in 

Sulphur,  crude            ........ 

112 

refined         ........ 

112 

sublimed     ........ 

•      H3 

precipitated          ....... 

•      H3 

coppered     ........ 

•      H3 

Pyrites     .......... 

114 

CHAP.  III.  —  Fertilisers         ........ 

•      "7 

General  methods        ......... 

.      118 

Preliminary  tests       ........ 

.      118 

Determination  of  moisture          ...... 

.      119 

,,                  nitrogen           ...... 

120 

phosphoric  acid       ..... 

•      i*3 

,,                  potash   ....... 

.    124 

Special  part     .......... 

125 

Nitrogenous  fertilisers       ........ 

•        125 

Ammonium  sulphate    ........ 

•        125 

Sodium  nitrate     ......... 

.        126 

Other  nitrates  ......... 

.        128 

Calcium  cyanamide       ........ 

.        128 

Phosphatic  fertilisers         ........ 

.        128 

Phosphates            ......... 

.        128 

Superphosphates  ......... 

.        130 

Slags  .          

I  \Z 

Precipitated  phosphate           ....... 

•    134 

Potash  fertilisers      ......... 

•    134 

Complete  analysis      ........ 

•    134 

Determination  of  the  sodium  chloride         .... 

•    135 

Complex  fertilisers  ......... 

.   136 

Stable  manure      ......... 

.   136 

Other  complex  fertilisers        ....... 

•    137 

xii  CONTENTS 

PAGE 

CHAP.  IV. — Cement   Materials    .  .  .  .  .  .  .  .138 

Limestones  and  marls  .          .          .          .          .          .  .  .138 

Partial  analysis          .          .          .          .          .          .          .  .  .139 

Complete  analysis      .          .          .          .          .          .          .  .  .139 

Clays  ............      144 

Pozzolane  and  slags      .          .          .          .          .          .          .  .  .146 

Chemical  analysis      .          .          .          .          .          .          .  .  .146 

Technical  tests  .          ,          .          .          .          .          .  .  .147 

Table  IV.     Compositions  of  pozzolane  and  the  like  .  .150 

Lime  .          .          .          .          .          .          .          .          .          .  .  .151 

Hydraulic  limes  and  cements         .          .          .          .          .  .  .152 

Chemical  analysis      .          .          .          .          .          ..  .  .152 

Technical  tests  .          .          .          .          .          .          .  .  .152 

Gypsum.  .  .......      157 

Table  V.     Compositions  of  hydraulic  limes      .          .  .  .158 

Table  VI.  ,,  quick-setting  cements  .  159 

Table  VII.  ,,  slow-setting  cements       .  .  .160 


CHAP.  V. — Metals    and  Alloys     .  .  .  .  .  .  .  .162 

Iron        .          .          .          .          .          .          .          .          .          .          .          .      162 

Determination  of  the  carbon      .  .  .  .  .  .  .163 

,,  „       silicon       .          .          .          .          .          .          .171 

,,  ,       manganese         .          .          .          .          .          .172 

,,  ,,       phosphorus        ......      173 

,,  ,,       sulphur    .  .  .  .  .  .  .176 

,,  ,,       arsenic     .......      179 

Table  VIII 181 

Special  steels  ..........      182 

Qualitative  tests        .          .          .          .          .          .          .          .          .182 

Chrome  steels       ..........      183 

Table  IX       .  185 

Nickel  steels          .          .          .          .          .          .          .          .          .          .186 

Table  X 187 

Manganese  steels.          .          .          .          .          .          .          .          .          .187 

Table  XI 188 

Tungsten  steels    .          .          .          .          .          .          .          .          .          .188 

Vanadium  steels  .          .          .          .          .          .          .          .          .          .      189 

Table  XII 191 

Molybdenum  steels        .          .          .          .          .          .          .          .          .191 

Silicon  steels         ..........      193 

Chrome-nickel  steels     .          .          .          .          .          .          .          .          .193 

Chrome- tungsten  steels  .          .          .          .          .          .          .  193 

Table  XIII 194 

Chrome- vanadium  steels        .          .          .          .          .          .          .          .194 

Table  XIV 194 

Ferro- metallic  alloys         .          .          .          .          .          .          .          .  195 

Ferro-silicon          ..........      195 

Table  XV 197 

Ferro-manganese  and  spiegeleisen  .          .          .          .          .          .          .197 

Silicon-ferro-manganese          .          .          .          .          .          .          .          .202 

Ferro-chrome         .  .  .  .          .  .  .  .  .  .202 

Table  XVI 203 

Ferro-tungsten      .  .  .  .  .  .  .  .  .  .204 

Table  XVII 205 

Ferro- vanadium    .  .  .  .  .  .  .  .  .  .205 

Table  XVIII  206 


CONTENTS  xiii 

PAGE 

Ferromolybdenum         .  .  .  .  .  .  .  .  .206 

Table  XIX .206 

Ferrotitanium      ........  .207 

Table  XX     ....  .208 

Ferro-aluminium  .          .          .          .          .          .          .          .          .208 

Electrolytic  analysis  of  metals  .          .          .          .          .          .          .209 

Copper  and  its  alloys       .....  .214 

Copper          .......  .214 

Table  XXI .220 

Phosphor-copper  .          .          .          .          .          .          .          .          .          .221 

Cupro  silicon          .  .  .  .  .  .  .          .  .  .221 

Cupro-manganese  .          .          .          .          ..          .          .          .222 

Ordinary  brasses  .  .  .  .  .  .  .  .  .224 

Table  XXII 227 

Special  brasses     .          .          .          .          .          .          .          .          .          .227 

Lead  brass        ..........     228 

Tin  brass 228 

Manganese  brass        .          .          .          .          .          .          .          .          .228 

Table  XXIII .228 

Iron  brass         ..........     229 

Aluminium  brass        .........      229 

Complex  brasses  .          .          .          .          .          .          .          .          .          .229 

Ordinary  bronzes  .........      232 

Special  bronzes    .          .          .  .          .          .          .          .          .     236 

Phosphor-bronzes       .  .  .  .          .  .  .  .  .236 

Silicon  bronzes.          .          .          .          .          .          .          .          .          .237 

Table  XXIV 237 

Lead  bronzes     .          .          .          .          .          .          .          .          .          .237 

Table  XXV 238 

Manganese  bronzes    .........     238 

Table  XXVI 239 

Nickel  bronzes  .........     239 

Lead-nickel  bronzes  .          .          .          .          .          .          .  .     239 

Aluminium  bronzes    .          .          .          .          .          .          .          .          .240 

Table  XXVII 241 

Zinc  and  its  alloys.          .........     241 

Zinc    .          .          .          .          .          .          .          .          .          .          .          .     241 

Table  XXVIII       . 243 

Zinc  dust    ...........     243 

Lead  and  its  alloys  .........     244 

Lead  ............     244 

Table  XXIX 247 

Hard  lead  ..........     247 

Partial  analysis          .          .          .          .          .          .          .          .          .247 

Complete  analysis      .          .          .          .          .          .          .          .          .248 

Table  XXX 250 

Antimony  and  its  alloys.          .          .          .          .          .          .          .          .250 

Antimony    ...........     250 

Table  XXXI 252 

Tin  and  its  alloys  .          .          .          .          .          .          .          .          .          .     252 

Tin 252 

Table  XXXII 254 

Tin-plate     ...........     254 

Phosphor- tin         .          .          .          .          .          .          .          .          .          .257 

Lead-tin  alloys     ..........     258 

Tin-foil         ...........     260 

White  metal         .          .  260 


xiv  CONTENTS 

PAGE 

Alloys  with  a  tin-antimony  basis        .          .          .          .          .          .261 

,,  ,,       lead- tin-antimony  basis         .          .          .          .          .264 

,,  ,,       lead- antimony  basis      ......     265 

Table  XXXIII 265 

Nickel  and  its  alloys        .          .          .          .          .          .          .          .          .266 

Nickel  ...........     266 

Table  XXXIV 268 

German  silver       .          .          .          .          .          .          .          .          .          .      268 

Table  XXXV 270 

Imitation  plate    ..........     271 

Aluminium  and  its  alloys         .          .          .          .          .          .          .          .271 

Aluminium  ..........      272 

Table  XXXVI 276 

Aluminium-copper  alloys       .          .          .          .          .          .          .          .276 

Aluminium-magnesium  alloys         .          .          .          .          .          .          .276 

Silver  and  its  alloys         .          .          .          .          .          .          .          .          .277 

Silver  alloys          .          .          .          .          .          .          .          .          .          .277 

Gold  and  its  alloys  .........     286 

Gold-copper  alloys         .          .          .          .          .          .          .          .          .286 

Gold-silver-copper  alloys        ........ 

Metallic  coavings      .......... 

Gilding         ........... 

Silver-plating        .......... 

Nickel-plating       .......... 

Tin-plating  .......... 

Zinc-plating  .   .       . 

Lead-plating          .......... 

Aluminium-plating         ......... 

Copper-plating      .......... 

Brass-plating         .......... 

Oxidising      ........... 

CHAP.  VI. — Fuels         ..........  297 

General  methods        ..........  298 

Chemical  analysis      .          .          .          .          .          .          .          .          .298 

Determination  of  calorific  power         ......  300 

Special  part    ...........  308 

Charcoal       ...........  308 

Peat 308 

Lignite         ...........  309 

Coal    ............  309 

Table  XXXVII.     Composition  of  lignites         .          .          .          .310 

Table  XXXVIII.     Limits  of  composition  of  coals  .          .          .  311 

Table  XXXIX.     Compositions  of  coals  .....  312 

Coke 315 

Agglomerated  fuels       .          .          .          .          .          .          .          .          •  3*5 

CHAP.  VII. — Goal-tar   and    its  Products       .  .  .  .  .  .317 

Crude  tar     .          .          .          .          .          .          .          .          .          .          -317 

Crude  light  tar  oils       .          .          .          .          .          .          .          .  319 

Middle  and  heavy  tar  oils    .          .          .          .          .          .          .          .320 

Anthracene  oils    ..........     320 

Pitch  .          .          .          .          .          .          .          .          .          .          .          -321 

Impregnating  oils  .  .          .          .          .  .  .  .          .322 

Benzoles       .          .          .          .          .          .          .          .          .          .          .     323 

Table  XL.     Characters  and  compositions  of  certain  benzoles   .      327 
Naphthalene         ..........     327 

Anthracene.          ..........     328 


CONTENTS  xv 

PAGE 

Carbolic  acid         ..........      330 

Pyridine       ...........      332 

CHAP.  VIII. — Mineral  Oils  and  their  Derivatives          ....  334 

Crude  petroleum            .          .          .          .          .          .          .          .          •  -334 

Physical  tests   ..........  334 

Chemical  tests .           .........  337 

Light  mineral  oils  (benzines)          .......  340 

Lighting  oil                                                              .          .                    .          .  343 

Physical  tests  ..........  343 

Table  XLI.     Factors  for  photometric  units     .          .          .          .346 

Chemical  tests            .........  347 

Middle  oils  (gas  oils)    .........  3-19 

Heavy  oils  (lubricating  oils)  .          .          .          .          .          .          .350 

Physical  tests  ..........  350 

Chemical  tests            .........  355 

Residues       .          .          .          .          .          .          .          .          .          .          .  360 

Vaseline       ...........  360 

Paraffin  wax         ..........  362 

Ceresine       ...........  363 

Montan  wax         ..........  365 

Lubricants             ..........  365 

Stiff  lubricants.          .          .          .          .          .          .          .          .          .365 

Emulsive  lubricants            ........  368 

CHAP.  IX.- — Fatty    Substances     .          .          .          .          .          .          .          .     370 

General  methods        .          .          .          .          .  .  .  .  .  -37° 

Preparation  of  the  sample  and  preliminary  determinations.          .     370 
Objective  characters.          .          .          .          .          .          .          .          .371 

Specific  gravity          .........      371 

Melting  and  solidifying  points   .          .          .          .          .          .          .372 

Saponification  .          .          .          .          .          .          .          .          .          -373 

Behaviour  towards  solvents        .          .          .          .          .          .          -373 

Acid  number    ..........     "374 

Saponification  number        .          .          .          .          .          .          .          -375 

Ester  number  .          .     ,     .          .          .          .          .          .          .          .     376 

Volatile  acid  number          .          .          .          .          .          .          .          -377 

Acetyl  number  .          ........     378 

Iodine  number .          .          .          .          .          .          .          .          .          •     3  79 

Absolute  or  "inner"  iodine  number.          .          .          .          .          .381 

Insoluble  or  fixed  fatty  acid  number  .          .          .          .          .382 

Hydroxy-acids  .          .          .          .          .          .          .          .          -383 

LactoneS  or  internal  anhydrides          .          .          .          .          .          -383 

Determination  of  the  glycerine.  .          .          .          .          .          .384 

,,  ,,         solid  and  liquid  fatty  acids        .  .  .384 

Table  XLII.     Stearic  and  palmitic  acids  from  the  acid  number     387 

Table  XLIII.     Palmitic  and  stearic  acids  from  the  melting  point     387 

Unsaponifiable  substances.          .......     388 

Detection  and  determination  of  resin          .....     390 

Maumene  number      .          .          .          .          .          .          .          .          .391 

Drying  properties  of  oils  .  .          .          .          .          .          .  .392 

Colour  reactions         .........     393 

Elaidin  test       ..........     394 

Special  part    ...........     395 

Vegetable  oils  ..........     395 

Arachis  oil  ..........     395 

Colza  and  other  cruciferous  oils    .......     398 

Cottonseed  oil  .          .          .          .          .          .          .          .          .401 


xvi  CONTENTS 

PAGE 

Linseed  oil  ..........     403 

Almond  oil  ..........     405 

Olive  oil      ...........     406 

Castor  oil  ......  ....  408 

Table  XLIV.     Characters  of  vegetable  oils      .          .          .          .410 

Sesame  oil  ...........      412 

Vegetable  fats          .          .          .          .          .          .          .          .          .          .     413 

Cacao  butter  ..........  413 

Table  XLV.     Characters  of  vegetable  fats       .          .          .          .414 

Coco-nut  oil          ..........     416 

Palm  oil       ...........     416 

Palm-kernel  oil    .          .          .          .          .          .          .          .          .          .417 

Other  vegetable  oils     .          .          .          .          .          .          .          .          -417 

Animal  fats     .          .          .          .          .          .          .          .          .          .          .418 

Tallow 418 

Table  XLVI.  Balkan's  table  .  .  .  .420 

Oleomargarine  .  .  .  .  .  .  .  .  .  .420 

Hog's  fat .421 

Bone  fat  .  .  .  .  .  .  .  .  .  .  .  426 

Foot  oil 428 

Fish  and  other  marine  animal  oils  .......  428 

Table  XLVII.     Characters  of  terrestrial  animal  fats  and  oils    .      429 
Fish  and  blubber  oils  .........     430 

Cod-liver  oil  .  .  .  .  .  .  .  .  .  431 

Table  XLVIII.  Characters  of  marine  animal  oils  .  .  .  432 

Waxes 433 

Beeswax       ...........     434 

Wool  fat      ...........     439 

Crude  wool  fat  .........     439 

Purified  wool  fat  (Lanoline)        .......      439 

Spermaceti  ...........  440 

Table  XLIX.  Characters  of  waxes  .  .  .  .  .441 
Spermaceti  oil  ..........  442 

CHAP.  X. — Industrial  Products  from  the  treatment  of  Fatty  Matter 

Boiled  linseed  oil  .          .          .          .          .          .          .          .          .443 

Oxidized  oils  (Blown  oils)     ........     445 

Hardened  or  hydrogenized  oils     .          .          .          .          .          .          -446 

Turkey-red  oil      ..........     447 

Oleine   (Oleic  acid)         .........     449 

Table  L.     Proportion  of  stearine  in  oleine       .          .          .          .450 

Wool  fat  oleine    ..........     451 

Stearine  (Stearic  acid)  .          .          .          .          .          .          .          .451 

Wool  fat  stearine  .........      453 

Degras          .......  •      454 

Candles        ...........     456 

Soaps  ...........     458 

Glycerine      ...........      463 

Crude  glycerine          .........     464 

Pure         „  468 

Table  LI.     Specific  gravity  of  aqueous  glycerine      .          .          .     469 


CHAPTER  I 
WATERS 

POTABLE    WATERS 

In  order  to  judge  of  the  potability  of  a  water,  a  partial  or  complete 
analysis  is  made  according  to  circumstances. 

The  former  includes  qualitative  tests  for  ammonia,  nitrates  and  phos- 
phates, and  determinations  of  the  fixed  residue,  hardness  and  organic 
matter.  Complete  analysis  requires,  in  addition,  determinations  of  the 
dissolved  gases  and  of  the  various  mineral  components  (chlorine,  sulphuric 
acid,  silica,  lime,  magnesia,  alkalies,  etc.). 

In  either  case  great  importance  attaches  to  the  taking  of  the  sample 
and  the  observation  of  the  physical  characters  of  the  water. 

Taking  of  the  Sample. — The  sample  should  be  collected  in  a  new 
bottle  of  colourless  glass  with  a  ground  stopper.  This  is  washed  first  with 
pure  hydrochloric  acid,  then  repeatedly  with  ordinary  water  (the  bottle 
being  completely  filled  twice),  and  lastly  with  distilled  water,  and,  when 
the  sample  is  taken,  it  is  well  rinsed  with  the  water  to  be  analysed.  Corks 
may  be  used,  but  these  should  be  new  and  either  well  washed  with  the  par- 
ticular water  or,  better,  waxed.  Coloured  glass  bottles,  especially  after 
use,  are  to  be  excluded  absolutely,  as  also  are  earthenware  or  metallic 
vessels. 

To  take  a  sample  from  a  spring,  river,  reservoir,  or  well,  the  vessel  should, 
where  possible,  be  immersed  in  the  water,  care  being  taken  not  to  collect 
the  surface  layer  or  the  deposit  at  the  bottom. 

Where  another  vessel  is  used  to  transfer  the  water  to  the  bottle,  it  must 
be  thoroughly  cleaned  and  then  rinsed  with  the  water  itself. 

Before  taking  a  sample  from  a  tap  or  pump  the  water  in  the  pump  or 
in  the  tube  of  the  tap  must  be  run  away. 

In  the  case  of  a  spring,  the  surroundings  must  be  examined — the  nature 
of  the  soil  and  especially  any  cultivated  ground,  habitations,  cemeteries, 
or  other  possible  source  of  contamination  which  may  be  near. 

With  rivers  the  distance  from  the  source  and  the  course  (whether  through 
inhabited  or  industrial  districts,  etc.)  are  noted,  together  with  the  geological 
character  of  the  ground. 

In  the  case  of  wells  or  reservoirs,  observations  are  made  on  their  depth, 
the  kind  of  wall,  the  nature  of  the  sub-soil,  and  the  distance  from  sewers 
or  other  source  of  contamination. 

For  partial  analysis,  3-4  litres  of  water  are  sufficient,  whilst  complete 
analysis  requires  about  20  litres. 

A.C.  1  1 


2  POTABLE  WATERS 

Samples  should  be  kept  in  a  cold,  dark  place  and  be  analysed  as  soon 
as  possible. 

Physical  Characters. — The  colour,  clearness,  odour  and  taste  are 
noted. 

When  the  sample  is  taken,  its  temperature  and  that  of  the  surrounding 
air  are  observed.  The  reaction  towards  litmus  is  also  tested. 

If  the  water  is  turbid,  it  is  left  at  rest  until  clear  and  then  filtered  through 
a  dry  filter,  the  analysis  being  carried  out  on  the  filtrate.  If  the  insoluble 
residue  is  appreciable  in  amount,  it  is  weighed  on  a  tared  filter  and  its 
nature  investigated. 

1.    Partial  Analysis 

The  partial  analysis  of  a  potable  water  includes,  besides  observation 
of  the  above  physical  characters,  the  following  estimations. 

1.  Fixed  Residue. — In  a  platinum  dish  or  crucible  200  c.c.,  or  more 
if  the  proportion  of  mineral  matter  is  low,  of  the  water  are  evaporated  to 
dryness  on  a  water-bath  or  air-bath.     The  residue  is  dried  in  an  oven, 
first  at  100-105°  to  constant  weight,  and  then  at  180°  to  constant  weight. 

The  residue  dried  at  180°  is  then  heated  to  dull  redness  over  a  naked 
flame  to  see  if  it  blackens  or  emits  an  odour  of  burning  organic  matter. 
When  marked  blackening  is  observed,  the  calcination  is  continued  until 
all  the  carbon  is  burnt,  the  residue  being  then  moistened  with  ammonium 
carbonate  solution,  calcined  again  at  a  dull  red  heat  and  reweighed.  The 
difference  in  weight  between  the  residue  dried  at  180°  and  that  heated  to 
dull  redness  gives  approximately  the  quantity  of  non-volatile  organic  matter 
in  the  water. 

As  a  rule,  the  residue  dried  at  180°  is  expressed  in  grams  per  100  litres 
of  the  water. 

2.  Hadrness. — A  water  is  said  to  be  hard  when  it  dissolves  soap  badly 
and  does  not  cook  vegetables  well,  these  being  properties  dependent  essen- 
tially on  the  calcium  and  magnesium  salts  contained  in  the  water  ;    the 
degree  of  hardness  thus  represents  the  whole  of  the  calcium  and  magnesium 
salts  calculated  as  either  calcium  carbonate  or  oxide.     Total  hardness  is 
that  due  to  all  the  calcium  and  magnesium  salts  dissolved  in  the  water ; 
permanent  hardness,  that  due  to  such  of  these  salts  as  remain  in  solution 
after  the  water  is  boiled  ;  temporary  hardness,  that  due  to  those  salts  which 
are  precipitated  from  the  water  on  boiling,  that  is,  which  were  originally 
dissolved  as  bicarbonates. 

The  two  following  methods  are  commonly  employed  for  the  estimation 
of  hardness  : 

(a)   BOUTRON   AND   BOUDET'S   METHOD. 

This  requires  : 

(1)  A  solution  of  pure  calcium  chloride  containing  0-25  gram  CaCl, 
per  litre.1 

(2)  Soap  solution,  prepared  by  dissolving  in  the  hot  50  grams  of  white 

1  This  may  be  prepared  by  dissolving  0-2253  gram  of  pure  calcium  carbonate  in 
hydrochloric  acid  and  evaporating  repeatedly  to  dryness  to  expel  the  excess  of  acid, 


POTABLE  WATERS  3 

Castile  soap  in  800    grams  of   90%   alcohol,  filtering  and  adding  half  a 
litre  of  distilled  water  to  the  filtrate. 

(3)  Burette  containing  about  5  c.c.,  the  volume  occupied  by  2-4  c.c. 
being  divided  into  twenty-two  equal  parts,  each  representing  one  degree 
of  hardness  ;  above  the  zero  is  another  mark  up  to  which  the  burette  must 
be  filled  with  soap  solution  and  which  represents  the  small  quantity  of 
the  liquid  necessary  in  each  case  to  produce  froth,  but  not  taken  account 
of  in  the  calculation. 

(4)  Bottle  with  a  ground-in  stopper  and  marks  indicating  the  volumes, 
10,  20,  30  and  40  c.c. 

The  titre  of  the  soap  solution  is  first  ascertained  :  into  the  bottle  are 
poured  40  c.c.  of  the  calcium  chloride  solution  ar.d  into  this  the  soap  solution 
is  gradually  dropped  from  the  burette  (filled  to  the  division  above  the  zero 
point)  ;  at  intervals  the  bottle  is  closed  and  vigorously  shaken  up  and 
down.  When  such  shaking  produces  a  froth  5-6  mm.  high  at  the  surface 
of  the  liquid  and  this  persists  for  at  least  5  minutes,  addition  of  the  soap 
solution  is  discontinued.  The  soap  solution  is  normal  when  the  froth- 
production  requires  22  divisions  of  the  burette  (in  addition  to  that  above 
the  zero,  which  makes  23  in  all).  If  less  is  required,  the  soap  solution 
must  be  diluted  with  water,  and  if  more,  soap  must  be  added. 

When  40  c.c.  of  calcium  chloride  solution  correspond  exactly  with  22 
divisions  of  the  soap  solution,  the  total  hardness  of  a  water  may  be  deter- 
mined as  above,  40  c.c.  of  the  water  being  titrated  with  the  soap  solution 
until  a  froth  persistent  for  5  minutes  is  obtained ;  the  number  of  divisions 
of  the  burette,  calculating  from  zero,  represents  the  number  of  French 
degrees  of  hardness.  One  French  degree  corresponds  with  i  gram  of  CaCO, 
per  100  litres  ;  thus,  a  water  with  10  degrees  of  hardness  contains  10  grams  of 
calcium  and  magnesium  salts,  calculated  as  calcium  carbonate,  per  100  litres. 

If  the  soap  clots  during  the  test,  the  water  probably  contains  more 
than  30  degrees  of  hardness.  In  such  case,  the  estimation  is  repeated 
with  20,  10,  or  even  5  c.c.  of  the  water,  in  fact  with  such  a  quantity  that, 
when  a  persistent  froth  is  formed,  the  liquid  is  opalescent  but  without 
clots  ;  the  volume  of  water  used  is  diluted  to  40  c.c.  with  distilled  water. 
The  dilution  is,  of  course,  allowed  for  in  calculating  the  hardness. 

To  determine  the  permanent  hardness,  100  c.c.  of  water  are  boiled  in  a 
dish  or  flask  for  20-30  minutes  and,  when  cold,  made  up  to  the  original 
volume  with  distilled  water  and  filtered ;  the  hardness  of  the  filtrate  is 
determined  as  above. 

The  temporary  hardness  is  given  by  the  difference  between  the  total  and 
the  permanent  hardness. 

(6)   CLARK'S  METHOD,  modified  by  Faisst  and  Knauss. 
This  requires  : 

(1)  An  ordinary  50  c.c.  burette, 

(2)  A  bottle  holding  about  200  c.c.  with  a  ground  stopper  and  marked 
at  TOO  c.c. 

(3)  A  solution  of  crystallised  barium  chloride  containing  0^523  grarr\ 
of  BaClg,  2H2O  per  litre. 


POTABLE  WATERS 


(4)  Soap  solution  :  150  grams  of  ordinary  lead  soap  and  40  grams  of 
pure  dry  potassium  carbonate  are  triturated  in  a  mortar  until  homogeneous 
and  then  exhausted  with  96%  alcohol.  The  filtered  alcoholic  solution  is 
distilled  to  eliminate  the  solvent  and  of  the  residual  soap,  dried  on  a  steam- 
bath,  20  parts  are  dissolved  in  1000  parts  of  56%  alcohol.  The  soap  solu- 
tion thus  obtained  is  then  titrated  as  follows.  One  hundred  c.c.  of  the 
barium  chloride  solution  are  introduced  into  the  bottle,  the  soap  solution 
being  then  run  in  gradually  from  the  burette  and  the  bottle  closed  and 
shaken  from  time  to  time  until  a  froth  5-6  mm.  high,  persistent  for  5  minutes, 
is  formed.  The  soap  solution  is  then  either  diluted  with  56%  alcohol  or 
concentrated  by  addition  of  soap  until  exactly  45  c.c.  correspond  with  100 
c.c.  of  the  barium  chloride  solution. 

The  hardness  of  a  water  is  determined  similarly,  100  c.c.  of  the  water 
being  taken,  or,  with  very  hard  waters  which  produce  clots,  50,  20  or  10 
c.c.,  or,  in  general,  such  volume  as  requires  from  20  to  45  c.c.  of  the  soap 
solution  ;  this  volume  is  made  up  to  100  c.c.  with  distilled  water  before 
titration.1  The  result  obtained  is  then  corrected  for  the  dilution. 

If  the  water  is  very  rich  in  magnesium  salts,  it  is  well  to  wait  a  few 
minutes  after  each  addition  of  soap  solution  and  before  shaking  in  order 
that  all  the  magnesium  may  combine  with  the  soap. 

From  the  number  of  degrees  of  soap  solution  necessary  to  produce  a 
persistent  froth  with  100  c.c.  of  the  water  the  hardness  in  German  degrees  is 
calculated  by  means  of  Table  I.  One  German  degree  represents  i  gram 

TABLE  I 
Clark's  Hardness  Table,  compiled  by  Faisst  and  Knauss. 


Soap 
Solution 
used  in  c.c. 

Correspond- 
ing degrees 
of  hardness. 

Number  of  de- 
grees correspond- 
ing with  i  c.c. 
of  soap  solution. 

Soap 
Solution 
used  in  c.c. 

Correspond- 
ing degrees 
of  hardness. 

Number  of  de- 
grees correspond- 
ing with  i  c.c. 
of  soap  solution. 

3'4 

0'5 

^ 

26-2 

6-5 

1 

5'4 

i-o 

28-0 

7-0 

7'4 

i'5 

>•          0-250 

29-8 

7'5 

V        0-277 

9-4 

2-O 

j 

31-6 

8-0 

j 

xi-3 

2'5 

33'3 

8-5 

13-2 

3-0 

35'0 

9-0 

15-1 
17-0 

3'5 
4»o 

0.260 

36-7 
38-4 

9-5 
10-0 

0-294 

18-9 

4'5 

40-1 

10-5 

20-8 

5-o 

41-8 

II-O 

22-6 
24-4 

5'5 
6-0 

0-277 

43'4 
45'0 

n-5 

I2-O 

0-310 

1  To  judge  of  the  quantity  of  water  to  be  taken,  a  preliminary  test  is  made  by 
shaking  in  a  test  tube  20  c.c.  of  the  water  with  6  c.c.  of  the  soap  solution.  If  the  liquid 
becomes  opalescent,  100  c.c.  of  the  water  may  be  taken  ;  if  it  becomes  very  turbid, 
50  c.c.,  or,  if  it  gives  a  precipitate,  20  or  10  c.c.  according  to  the  amount  of  the  pre- 
cipitate. 


POTABLE  WATERS  5 

of  CaO  per  100  litres  of  water,  so  that  a  water  with  10  German  or  Clark 
degrees  will  contain  10  grams  per  100  litres  of  calcium  or  magnesium  oxide 
combined  with  carbonic,  sulphuric,  hydrochloric  and  nitric  acids.1 

If  the  number  of  c.c.  of  soap  solution  used  does  not  occur  in  the  table, 
the  corresponding  degree  of  hardness  is  determined  by  interpolation. 

Examples.  100  c.c.  of  a  water  required  39-8  c.c.  of  soap  solution  ;  the  nearest 
number  in  the  table  is  40-1,  corresponding  with  10-5  degrees  of  hardness.  Hence 

40-1  —  39-8        =0-3 
0-3  X    0-294    =  0-0882 
and  10-5  —    0-0882  =  10-4118, 
the  degree  of  hardness  being  therefore  10-41. 

Another  water  required  32-0  c.c.  of  soap  solution  ; 
32-0  —  31-6        =0-4 

0-4  X    0-277    =  0-1108 
and    8-0  -(-    0-1108  =  8-n 

The  permanent  and  also  the  temporary  hardness  are  determined  as 
under  (a). 

The  relations  between  French,  English,  and  German  degrees  of  hardness 
are  shown  in  the  following  table  : 

French  German  English 

degrees.  degrees.  degrees. 

I    French  degree                                           i  0-56  0-70 

i  German  degree     ....      1-79  i  1-25 

i  English  degree      .          .          .          .1-43  0-80                 i 

3.  Alkalinity. — By  the  alkalinity  of  a  water  is  meant  the  quantity  of 
calcium  and  magnesium  carbonates  and,  where  present,  alkali  carbonates 
present  in  the  water ;  it  is,  therefore,  related  to  the  hardness. 

Its  determination,  proposed  by  Wartha  and  Pfeiffer,  may  replace  that 
of  the  hardness,  especially  when  it  is  desired  to  compare  rapidly  a  number 
of  samples  of  water  or  to  detect  any  slight  variations  which  a  given  water 
may  undergo. 

According  to  Gigli,  the  alkalinity  of  a  water  (total,  permanent  and 
temporary)  is  easily  determined  as  follows  :  2 

100  c.c.  of  the  water  are  titrated  with  N/20 -hydrochloric  acid  in  presence 
of  2  drops  of  o-i  %  aqueous  methyl  orange  solution.  The  result  is  expressed 
as  CaCO3  per  litre  (i  c.c.  =  0-0025  gram  of  CaCO3)  and  represents  the  total 
alkalinity,  that  is,  the  alkali  and  alkaline  earth  carbonates. 

Another  100  c.c.  of  the  water  is  boiled  for  12  minutes  in  a  reflux  appara- 
tus, allowed  to  cool  and  filtered,  the  filter  being  washed  with  a  little  boiled, 
distilled  water  and  the  whole  of  the  filtrate  titrated  as  before.  From  the 
volume  of  N/2o-acid  used  in  this  second  determination  it  is  necessary  to 
subtract  that  required  to  neutralise  the  alkalinity  transferred  to  the  water 
from  the  glass  during  boiling,  this  being  determined  by  a  blank  test  with 
distilled  water.  Good  Jena  glass  produces  in  100  c.c.  of  water,  after  12 
minutes'  boiling,  an  alkalinity  corresponding  with  about  0-25  c.c.  of  N/2O- 
HC1. 

1  English  degrees  represent  grains  of  CaO  per  gallon  of  water,  that  is  grams  of  CaO 
per  70  litres. 

2  L'industria  chimica,  mineraria  e  metallurgica,  1914,  p.  289. 


6  POTABLE  WATERS 

The  result,  expressed  as  CaCO3  per  litre,  represents  the  permanent 
alkalinity  (due  to  magnesium  carbonate  and  alkali  carbonates). 

Finally,  the  difference  between  the  two  above  alkalinities  represents 
the  temporary  alkalinity,  that  is,  the  calcium  existing  as  bicarbonate,  which 
is  precipitated  as  carbonate  during  boiling. 

4.  Ammonia. — This   is   determined   by  means   of  Nessler's   solution 
prepared  by  dissolving  50  grams  of  potassium  iodide  in  50  c.c.  of  hot  water 
and  gradually  pouring  into  this  solution  concentrated  mercuric  chloride 
solution  until  the  red  precipitate  begins  to  refuse  to  redissolve  (20-25  grams 
of  mercuric  chloride  are  required).     To  the  filtered  liquid  is  added  a  solution 
of  150  grams  of  potassium  hydroxide  in  150  c.c.  of  water,  the  total  volume 
being  made  up  to  a  litre  with  distilled  water ;    5  c.c.  of  the  concentrated 
mercuric  chloride  solution  are  then  added  and  the  liquid  shaken  and  allowed 
to  stand,  the  clear  liquid  being  decanted  into  a  bottle  which  is  kept  tightly 
stoppered  with  a  rubber  bung  and  in  the  dark. 

One  hundred  c.c.  of  the  water  are  poured  into  a  glass  cylinder  with  a 
ground  stopper  and  0-5  c.c.  of  sodium  hydroxide  solution  (i  :  2)  and  i  c.c. 
of  sodium  carbonate  solution  (2-7  :  5)  added.  The  liquid  is  shaken  and 
then  allowed  to  stand,  the  clear  liquid  being  decanted  from  the  deposited 
precipitate  into  another  glass  cylinder  and  treated  with  1-2  c.c.  of  Nessler 
reagent.  The  formation  of  a  reddish-yellow  turbidity  or  precipitate  indi- 
cates that  the  water  contains  ammonia,  the  amount  of  the  latter  increasing 
with  the  intensity  of  the  turbidity  or  precipitation.1 

5.  Nitrous  Acid  (Nitrites). — Nitrites  are  detected  by  Griess' s reagent, 
comprising :     (i)   saturated   a-naphthylamine  hydrochloride  solution,    (2) 
saturated  sulphanilic  acid  solution,  and  (3)  10%  pure  hydrochloric  or  sul- 
phuric acid  solution. 

From  10  to  50  c.c.  of  the  water  are  introduced  into  a  glass  cylinder  with 
a  ground  stopper,  3  drops  of  the  sulphanilic  acid  solution,  i  drop  of  the 
hydrochloric  or  sulphuric  acid,  and  3  drops  of  the  a-naphthylamine  hydro- 
chloride  solution  being  successively  added.  The  presence  of  nitrite,  in  the 
water  is  indicated  by  a  coloration  varying  between  rose  red  and  deep 
red  according  to  the  proportion.2 

6.  Nitric  Acid  (Nitrates). — The  qualitative  test  for  nitrates  may  be 
made  with  the  ordinary  reagent  consisting  of  ferrous  sulphate  and  sul- 
phuric acid,  the  water  being  used  as  such  or  after  concentration  to  a  small 
volume. 

Traces  of  nitric  acid  may  be  detected  by  means  of  brucine  :  2-3  c.c. 
of  the  water  are  treated  in  a  porcelain  dish  with  a  crystal  of  brucine  and 
a  few  drops  of  concentrated  sulphuric  acid  free  from  nitric  acid  ;  the  presence 
of  nitrates  in  the  water  is  shown  by  a  red  coloration  rapidly  changing  to 
greenish-yellow.  For  the  quantitative  determination,  see  Complete  Analysis 

(5). 

7.  Phosphoric  Acid  (Phosphates). — 0:0  c.c.  of  the  water,  either  as 
such  or  after  concentration,  are  acidified  with  nitric  acid,  treated  with 

1  If  comparison  is  made  with  standard  ammonium  chloride  solutions,  the  quantity 
of  ammonia  (or  ammonium  salts)  in  the  water  may  be  calculated. 
1  This  method  may  similarly  be  rendered  quantitative. 


POTABLE  WATERS  7 

excess  of  ammonium  molybdate  solution,  heated  to  about  40°  and  stirred, 
and  examined  for  yellow  turbidity  or  precipitate. 

8.  Organic  Matter. — Indications  of  the  presence  of  organic  matter 
in  a  water  are  obtained  from  the  blackening  of  the  dry  residue  when  heated, 
provided  the  amount  present  is  marked.  For  quantitative  determination, 
recourse  is  had  to  the  indirect  method  of  oxidising  with  potassium  per- 
manganate and  calculating  the  oxygen  necessary  for  the  combustion  of 
the  organic  matter. 

The  methods  most  commonly  used  are  the  following  : 

(a)  KUBEL'S  METHOD,  which  requires  : 

(1)  Distilled  water  free  from  organic  matter,  obtained  by  redistilling 
water  with  a  little  permanganate. 

(2)  Pure  dilute  sulphuric  acid,  1:3. 

(3)  N/ioo-potassium  permanganate  solution,  containing  0-3163  gram 
of  KMnO4  per  litre. 

(4)  N/ioo-oxalic  acid,  containing  0-63  gram  of  H2C2O4,  2H2O  per  litre. 
The  last  two  solutions  should  correspond  volume  with  volume.     To 

check  this,  20  c.c.  of  the  oxalic  acid  solution  are  heated  nearly  to  boiling 
with  5  c.c.  of  the  sulphuric  acid  and  then  titrated  with  the  permanganate 
until  a  pink  coloration  persists  :  20  c.c.  should  be  required. 

To  100  c.c.  of  the  water  are  added  5  c.c.  of  the  sulphuric  acid  and  then 
10  or  more  c.c.  of  the  permanganate,  so  that  the  liquid  remains  coloured 
even  after  boiling.  The  liquid  is  boiled  for  5  minutes,  a  volume  of  the 
oxalic  acid  equal  to  that  of  the  permanganate  taken  being  then  added. 
The  solution,  which  is  then  colourless,  is  titrated  in  the  hot  with  perman- 
ganate. 

The  difference  between  the  total  volume  of  permanganate  used  and 
that  necessary  for  the  oxidation  of  the  oxalic  acid  added  (in  other  words 
the  volume  of  permanganate  used  in  the  final  titration)  gives  the  volume 
of  permanganate  consumed  in  the  oxidation  of  the  organic  matter.  Since 
i  c.c.  of" N/ioo -permanganate  corresponds  with  0-00008  gram  of  oxygen, 
the  number  of  c.c.  of  permanganate  consumed  must  be  multiplied  by  0-08 
to  obtain  the  grams  of  oxygen  used  up  in  oxidising  the  organic  matter  in 
100  litres  of  the  water.  On  the  assumption  that  i  part  of  permanganate 
oxidises  very  nearly  5  parts  of  organic  matter,  the  amount  of  the  latter 
per  100  litres  of  water  is  sometimes  calculated  by  multiplying  the  number 
of  c.c.  of  permanganate  used  up  by  1-58. 

(b)  SCHULZE  AND  TROMMSDORFp's  METHOD.     This  requires  the  same 
reagents  as  the  preceding  method,  together  with  pure  sodium  hydroxide 
solution  (i  :  2). 

One  hundred  c.c.  of  the  water  are  boiled  for  10-15  minutes  with  0-5  c.c. 
of  the  caustic  soda  solution  and  10  c.c.  of  the  permanganate,  allowed  to 
cool  to  about  60°,  mixed  with  5  c.c.  of  the  sulphuric  acid  and  10  c.c.  of  the 
oxalic  acid  solution,  and  titrated  with  the  permanganate.  The  oxygen 
consumed  and  the  organic  matter  present  are  then  calculated  as  described 
under  (a). 

With  either  of  these  methods  it  is  always  necessary  to  make  a  blank 


8 


POTABLE  WATERS 


test  with  distilled  water  and  to  make  allowance  for  any  permanganate 
consumed  thereby. 

2.    Complete  Analysis 

Complete  analysis  of  a  water  includes,  in  addition  to  the  determinations 
of  the  partial  analysis,  the  following  estimations. 

1.  Dissolved  Gases. — The  gases  usually  found  dissolved  in  water 
are  oxygen,  nitrogen  and  carbon  dioxide.  They  are  measured  by  extract- 
ing them  from  the  water  by  means  of  a  pump  or  by  boiling,  collecting  them 
in  a  graduated  vessel  and  measuring  their  total  volume.  The  carbon  dioxide 
is  then  absorbed  by  caustic  potash,  and  the  oxygen  by  alkaline  pyrogallol, 
the  nitrogen  remaining. 

The  apparatus  and  methods  used  for  estimating  gases  in  water  are  many, 
and  detailed  descriptions  of  them  may  be  found  in  special  treatises.1  One 
of  the  simplest  modes  of  procedure  consists  in  using  an  ordinary  nitrometer 

(Fig.  i). 

The  water  to  be  examined  is  collected  in  a  tared  half-litre  flask,  A, 

which  is  filled  completely  and  is  then  closed 
with  a  perforated  rubber  stopper  through 
which  passes  a  glass  tube  sealed  at  the 
lower  end  and  furnished  with  a  lateral 
orifice,  the  latter  remaining  within  the 
stopper  during  transport  so  that  the  flask 
is  kept  hermetically  sealed. 

The  full  flask  is  weighed  to  give  the 
amount  of  water  taken  and  is  then  arranged 
on  a  gauze  over  a  burner  and  connected 
with  the  nitrometer,  B,  by  means  of  the 
tube  a.  The  nitrometer  should  be  filled 
with  previously  boiled,  saturated  sodium 
chloride  solution,  which  is  also  used  to  fill 
the  small  tube  in  the  stopper  of  the  flask 
and  the  whole  of  the  tube  a,  so  that  no 
bubble  of  air  remains  in  the  apparatus.  By 
means  of  a  T-piece  inserted  in  the  tube  a  at 
c,  it  is  easy,  by  opening  the  clips  at  b  and  c  to  fill  the  whole  with  the  salt 
solution  in  the  nitrometer. 

When  all  is  ready,  the  small  tube  is  forced  down  until  its  lateral  orifice 
is  below  the  stopper  of  the  flask,  the  clip  b  is  opened  and  the  flask  heated, 
the  liberated  gases  collecting  in  the  nitrometer.  During  all  this  time  the 
bulb,  C,  of  the  nitrometer  is  kept  down.  When  evolution  of  gas  ceases, 
the  clip  b  is  closed,  the  bulb  C  raised  until  the  level  of  the  liquid  in  it  corre- 

1  For  instance,  Frankland,  Water  Analysis  (London,  1880);  Tiemann  und  Gaert- 
ner,  Die  chemische  und  bakteriologische  Untersuchung  de*  Wassers,  4th  edit.  (Brunswick, 
1893);  Ohlmuller,  Die  Untersuchung  und  Beurteilung  des  Wassers  und  Abwassers  : 
Leitfaden  fur  die  Praxis  und  zum  Gebrauch  im  Laboratorium  (1910)  ;  Pearmain  and  Moor, 
The  Chemical  and  Biological  Analysis  of  Water  (London,  1899)  ;  Lunge,  Technical 
Methods  of  Chemical  Analysis  (London,  1908).  Fresenius,  Quantitative  Analysis ; 
Guareschi,  Nuova  enciclopedia  di  chimica,  Vol.  Ill  (Turin,  1901). 


FIG.  I. 


£Of  ABLE  WATERS  9 

spends  with  that  in  the  nitrometer  tube,  and  the  volume  of  gas  read  off, 
the  temperature  and  barometric  pressure  being  observed.  The  bulb  C  is 
then  lowered  and  concentrated  caustic  potash  solution  introduced  into  the 
nitrometer  by  means  of  the  funnel  D  and  the  tap  d,  care  being  taken  to  avoid 
entry  of  air.  The  instrument  is  then  well  shaken  so  that  the  caustic  potash 
may  absorb  the  carbon  dioxide  and  the  volume  of  the  remaining  gas  read 
off  after  the  two  levels  of  the  liquid  have  been  brought  into  agreement  by 
raising  C.  These  operations  are  subsequently  repeated  after  a  freshly 
prepared  concentrated  solution  of  pyrogallol  in  excess  of  potassium  hydroxide 
has  been  introduced  into  the  nitrometer,  the  latter  being  left  for  about  an 
hour  after  shaking  in  order  that  all  the  oxygen  may  be  absorbed.  The 
volume  of  the  residual  gas  is  then  read  with  the  usual  precautions. 

The  first  reading  gives  the  total  volume  of  the  three  gases,  CO2  +  N  +  O, 
the  second  the  volume  of  N  +  0  and  hence,  by  difference,  the  CO2,  and 
the  third  the  N  and  therefore,  by  difference,  the  O.  The  volumes  thus 
obtained  must  be  reduced  to  the  temperature  o°  and  the  pressure  760  mm., 
this  being  done  by  means  of  the  formula, 


760   (i  +  0-00367  t)' 

where  F  is  the  volume  of  gas  at  o°  and  760  mm.,  v  the  volume  actually  read 
off,  P  the  barometric  pressure,  p  the  correction  of  the  pressure  for  the 
temperature  t  (found  from  suitable  tables),  /  the  correction  of  the  pressure 
for  the  water  vapour  (from  tables),  and  t  the  temperature.  Finally  the 
volumes  of  the  different  gases  are  calculated  per  100  litres  of  the  water. 

2.  Carbonic  Anhydride.  —  As  a  rule,  estimations  are  made  of  the 
total  carbon  dioxide,  that  in  the  free  state  and  that  semi-combined,  i.e., 
existing  as  bicarbonates. 

(a)  TOTAL  CARBON  DIOXIDE.  To  o'5  or  i  litre  of  the  water,  collected 
so  that  no  trace  of  gas  escapes  in  a  flask  which  is  almost  completely  filled,1 
are  added  5-10  c.c.  of  concentrated  ammoniacal  calcium  chloride  solution,2 
the  flask  being  then  closed  tightly  with  a  rubber  stopper.  After  some  time 
(24  hours  or  more)  the  water  is  heated  on  a  steam-bath,  access  of  air  being 
avoided  as  far  as  possible  ;  it  is  then  filtered  rapidly,  the  filter  being  kept 
covered  with  a  glass.  The  precipitate  of  calcium  carbonate  is  washed  with 
boiled  water  until  ammonium  oxalate  fails  to  render  the  wash  water  turbid. 
Any  calcium  carbonate  adhering  to  the  walls  of  the  flask  is  dissolved  in  a 
little  dilute  hydrochloric  acid  and  the  solution  and  water  used  for  sub- 
sequent washing  out  of  the  flask  placed  in  a  small  beaker,  where  the  calcium 
carbonate  is  reprecipitated  by  addition  of  hot  sodium  carbonate  solution  ; 
this  precipitate  is  filtered  on  the  original  filter  and  the  whole  washed  until 
the  wash  water  is  no  longer  alkaline. 

The  filter  with  the  calcium  carbonate  is  introduced  into  an  apparatus 
for  the  determination  of  carbon  dioxide  (see  chapter  on  Cement  Materials). 
The  weight  of  C02  found  is  then  referred  to  100  litres  of  water. 

1  It  is  convenient  to  use  a  flask  tared  with  its  rubber  stopper,  and  to  weigh  it  after 
nearly  filling  it  with  the  water  ;    from  the  weight  of  the  water  the  volume  may  be 
obtained  by  dividing  by  the  density. 

2  This  operation  is  best  carried  out  where  the  water  is  collected. 


10  POTABLE  WATERS 

(b)  FREE  AND  SEMI-COMBINED  CARBON  DIOXIDE.  To  200  c.c.  of  the 
water  are  added  25  c.c.  of  N/io-baryta  solution  and  2  c.c.  of  highly  con- 
centrated calcium  chloride  solution.  The  mixture  is  left  for  some  hours 
in  a  tightly  closed  vessel ;  100  c.c.  of  the  liquid  are  then  drawn  off  and 
the  excess  of  baryta  present  determined  with  decinormal  hydrochloric  acid 
and  phenolphthalein.  The  number  of  c.c.  of  acid  used  is  multiplied  by  2^27 
since  the  total  volume  of  the  liquid  was  227  c.c.  ;  the  product  is  subtracted 
from  the  number  of  c.c.  of  acid  necessary  to  neutralise  25  c.c.  of  the  baryta, 
and  the  difference,  being  equivalent  to  the  baryta  precipitated  by  the  free 
and  semi-combined  carbon  dioxide,  when  multiplied  by  0^0022  gives  the 
free  and  semi-combined  carbon  dioxide  in  200  c.c.  of  the  water. 

3.  Chlorine  (Volhard's  method). — To  50  or  looc.c.  of  the  water,  acidi- 
fied with  nitric  acid,  is  added  more  than  sufficient  decinormal  silver  nitrate 
solution  to  precipitate  all  the  chlorine  (usually  5  or  10  c.c.  suffice)  ;    the 
liquid  is  shaken,  allowed  to  settle,  and  filtered,  both  the  precipitating  vessel 
and  the  filter  being  well  washed.1    To  the  filtered  liquid  are  added  a  few 
drops  of  ferric  alum  solution  and  a  little  nitric  acid,  the  excess  of  silver 
being  then  determined  by  titration  with  N/io  ammonium  thiocyanate 
solution  until  a  pinkish-yellow  coloration  appears.     The  difference  between 
the  volume  of  silver  nitrate  taken  and  that  of  the  thiocyanate  required  to 
precipitate  the  excess  of  silver,  multiplied  by  0-00355,  gives  the  amount 
of  chlorine  in  grams  in  the  volume  of  water  taken. 

4.  Sulphuric  Acid.— 200  c.c.  or  more   (up  to  i  litre)  of  the  water, 
according  as  it  is  rich  or  poor  in  sulphates,  are  acidified  with  hydrochloric 
acid  and  evaporated  to  small  volume  (100-150  c.c.),  theTiquid  being  then 
treated  with  barium  chloride,  heated,  allowed  to   deposit,  and  filtered ; 
the  precipitated  barium  sulphate  is  washed  with  water,  dried,  calcined 
(the  filter  paper  being  burned  separately),  and  weighed  :  i  part  of  BaSO4  = 
0*3433  part  SO3. 

5.  Nitric  Acid. — One  litre  of  the  water  is  evaporated  to  a  few  c.c. 
and  the  nitric  acid  then  determined  by  one  of  the  ordinary  methods  (see 
Fertilisers  :    Determination  of  Nitric  Acid). 

6.  Phosphoric  Acid.— One  litre  or  more  of  the  water  is  evaporated 
to  a  small  volume,  in  which  the  phosphoric  acid  is  estimated  by  precipita- 
tion as  ammonium  phosphomolybdate  (see  Fertilisers  :    Determination  of 
the  total  Phosphoric  Acid). 

7.  Silica. — One  or  more  litres  of  the  water,  according  to  the  amount 
of  the  fixed  residue,  are  evaporated  to  dryness  in  a  platinum  dish,  the 
residue  being  dried  at  105°,  treated  with  hydrochloric  acid,  evaporated 
again  and  dried  at  105°.     It  is  then  treated  with  hydrochloric  acid  and 
water  and  the  liquid  filtered,  the  silica  being  washed,  dried,  calcined,  and 
weighed  as  SiO2. 

8.  Iron  and  Aluminium. — The  filtrate  from  the  preceding  operation 
is  treated  with  a  little  ammonium  chloride  and  a  slight  excess  of  ammonia 
and  heated ;    if  a  precipitate  is  formed,  this  is  filtered  off,  washed,  dried, 
calcined,  and  weighed ;    it  represents  Fe2O3  +  A12O3. 

1  To  save  time,  after  the  silver  nitrate  is  added  the  liquid  is  made  up  to  a  known 
volume  and  filtered,  an  aliquot  part  being  taken  for  the  titration  of  the  excess  of  silver. 


II 

9.  Lime. — The  filtrate  from  the  preceding  operation  is  concentrated 
'to  some  extent  and  treated  with  ammonia  and  ammonium  oxalate ;    the 

calcium  oxalate  formed  is  filtered  off,  washed,  dried,  and  strongly  heated 
in  the  blowpipe  flame  until  it  undergoes  no  further  loss  of  weight ;  this 
represents  CaO. 

10.  Magnesia. — The  filtrate  from  the  calcium  oxalate  is  evaporated 
to  dryness  in  a  platinum  dish  and  the  residue  genily  heated  to  expel  all 
the  ammonium  salts  and  then  redissolved  in  very  dilute  hydrochloric  acid. 
The  solution  is  neutralised  with  ammonia  solution  and  treated  with  neutral 
ammonium  carbonate  solution  in  such  amount  that  the  precipitate  at  first 
formed  redissolves.     The  liquid  is  then  left  for  12  hours  to  allow  of  the 
complete  precipitation  of  the  magnesium  as  magnesium  ammonium  car- 
bonate, which  is  filtered  off,  washed  with  dilute  ammonium  carbonate 
solution,  dried,  calcined,  and  weighed  as  magnesia  (MgO). 

11.  Alkalies. — The  filtrate  from  the  previous  operation  is  evaporated 
to  dryness  with  ammonium  chloride  in  a  platinum  dish,  the  residue  being 
carefully  calcined  and  the  pure  alkali  chlorides  remaining  then  weighed. 
If  the  chlorine  is  estimated,  the  amounts  of  K2O  and  Na2O  present  may 
be  calculated  (see  Fertilisers  :    Stassfurt  Salt). 

12.  Poisonous  and  other  Metals. — The  residue  from  the  evaporation 
of  some  litres  of  the  water  may  be  tested  for  the  poisonous  heavy  metals, 
such  as  lead,  copper,  barium,  etc.,  and  for  elements  found  only  in  traces 
in  potable  waters,  such  as  boron,  iodine,  bromine,  lithium,  etc. 

13.  Calculation  of  the  Analytical  Results. — As  a  rule  the  amounts 
of  the  different  constituents  are  referred  to  i  litre  or  100  litres  of  the  water, 
all  the  elements  estimated  being  expressed  as  oxides  with  the  exception 
of  chlorine. 

To  check  the  results  the  amounts  of  the  metallic  oxides  (Na2O,  CaO, 
MgO)  and  of  the  acid  anhydrides  (S03,  N2O5,  SiO2,  CO2)  and  chlorine  are 
added  together,  an  amount  of  oxygen  equivalent  to  the  chlorine  being 
subtracted  from  the  sum  ;  the  remainder  should  be  sensibly  equal  to  the 
fixed  residue  dried  at  180°. 

The  salts  contained  in  the  water  may  be  reconstructed  by  uniting  the 
bases  and  acids  in  their  most  probable  combinations.  The  chlorine  is 
first  combined  with  the  sodium  and  any  excess  (rare)  with  calcium.  The 
sulphuric  acid  is  united  with  the  lime  and  the  nitric  acid  with  the  potash 
and  lime,  or  with  the  ammonia  (if  such  is  present).  The  rest  of  the  lime, 
magnesia  and  potash  is  united  with  the  carbon  dioxide  ;  the  silica  remains 
free. 

If,  however,  the  evaporated  water  exhibits  an  alkaline  reaction,  it 
contains  sodium  carbonate,  generally  together  with  sulphate  and  chloride ; 
the  lime  and  magnesia  are  then  all  combined  with  carbon  dioxide. 

* 
*   * 

A  water  may  be  said  to  be  potable  when  it  is  clear,  colourless,  odourless,  of 
pleasant  taste,  cool  and  of  constant  temperature  and  does  not  contain  more 
than  certain  limiting  proportions  of  various  dissolved  matters.  According  to 
different  authors,  these  limits  are  as  follows  : 


12  WATER  FOR  INDUSTRIAL  PURPOSES 

Per  100  litres. 
Lime,  CaO  .          .          .          .          .          .          .  up  to  12  grams 

Magnesia,  MgO    .......,,         4 

Sulphur  trioxide,  SO3  ......,,      0-2-10  ,, 

Chlorine,  Cl  .......,,       o-2-3-5,, 

Nitric  anhydride,  N2O5          .          .          .          .          .     0-4-2 '7  ,, 

Nitrous  anhydride,  N2O3       .....  o 

Ammonia,  NH3  .          .          ...          .          .  o 

Solid  residue  at  180°   .          .          .          .          .          .     10-50 

Total  hardness,  in  French  degrees          .          .  up  to  32         ,, 

Organic  matter  (oxygen  consumed)        .          .          .      up  to  0-25      ,, 

As  is  seen  from  this  table,  to  be  potable  a  water  should  first  be  quite  free 
from  ammonia  and  nitrites,  and  should  contain  only  small  proportions  of  nitrates 
and  chlorine  and  a  very  small  amount  of  organic  matter  (expressed  as  oxygen 
absorbed).  These  substances  are  mainly  considered  because,  although  they 
are  quite  harmless  in  the  small  proportions  in  which  they  always  occur  in  water, 
their  presence  demonstrates  that  the  water  was  formerly  or  is  still  contaminated 
by  organic  matter  (sewage  water,  drainings  from  inhabited  districts,  etc.).  A 
water  containing  ammonia  or  nitrites  or  organic  matter  (beyond  the  limiting 
amount)  should  always  be  rejected.  A  water  containing  nitrates  or  chlorine 
beyond  the  established  limits  should  be  suspected,  unless  it  can  be  proved 
definitely  that  these  salts  come  from  the  soil.  The  presence  of  phosphoric  acid 
is  also  a  sign  of  the  organic  contamination  of  water.  In  special  cases  as  much 
as  5-0  grams  of  chlorine  per  100  litres  may  be  tolerated,  so  long  as  the  water 
exhibits  no  other  defect. 

Table  II  gives  the  compositions  of  the  water  supplies  of  various  towns. 

WATER  FOR  INDUSTRIAL  PURPOSES 

Waters  for  use  in  industries,  for  steam  boilers,  laundries,  factories  of 
different  kinds,  are  examined  especially  with  reference  to  their  content  of 
lime  and  magnesium  salts.  With  such  waters  it  is  required  to  know  the 
content  of  lime,  magnesia,  sulphuric  acid,  and  carbonic  acid.  Further, 
the  quantities  of  lime  and  sodium  carbonate  necessary  to  correct  any  exces- 
sive hardness  of  the  waters  must  be  known.  The  addition  of  lime  is  neces- 
sary to  transform  the  calcium  bicarbonate  into  carbonate,  to  saturate  the 
free  carbonic  acid  and  to  precipitate  the  organic  matter  ;  that  of  soda  is 
required  to  decompose  the  calcium  sulphate.  To  eliminate  the  latter  and 
sulphates  in  general,  barium  chloride  may  also  be  used. 

In  practice  use  has  been  made  and  is  still  made  of  the  results  of  the 
hardness  determination  (see  Potable  WTaters  :  Partial  Analysis,  2),  but 
this  test  gives  only  approximate  and  sometimes  unexpected  results,  since 
it  furnishes  no  information  concerning  the  relation  between  lime  and  mag- 
nesia, or  between  carbonates  and  sulphates.  To  obtain  reliable  data  it  is 
necessary  to  carry  out — besides  various  qualitative  tests  to  ascertain  if 
the  water  is  more  or  less  rich  in  lime,  magnesia,  carbonates,  sulphates,  or 
chlorides — the  different  determinations  indicated  for  potable  waters  (see 
Potable  Waters,  Complete  Analysis,  2,  3,4,  9  and  10),  or  at  least  the  following 
tests  suggested  by  Lunge  *  and  recognised  as  of  technical  value. 

1.  Volumetric  Estimation  of  the  Total  Alkalinity. — Two  hundred 
c.c.  of  the  water  are  titrated  in  the  cold  with  N/5-hydrochloric  acid  in  pres- 

Lunge,  Technical  Methods  o!  Chemical  Analysis  (London,  1908),  Vol.  I.  p.  800. 


WATER  FOR  INDUSTRIAL  PURPOSES 


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Description. 

Upland  Surface  Waters. 

Cardiff  Supply,  Dec.,  1908  
Aberdeen  Supply,  River  Dee,  March,  1910  . 
Glasgow,  Loch  Katrine,  Nov.,  1891  . 

JLiverpooi,  vyrnwy  water,  .average  ior  1903 
Birmingham,  Elan  Valley  Water,  Jan.,  1911 
Belfast,  Woodburn  Supply,  Jan.,  1910 

Deep  Well  and  Spring  Waters. 

Portsmouth  :  from  Chalk  Springs,  Aug.,  1905 
Nottingham  :  New  Red  Sandstone,  Dec.,  1910  . 

.Liverpool  :  JNew  Kea  banastone,  1903 
Eastbourne  :  Chalk,  1911  
Great  Grimsby  :  Chalk,  1911  

a 

iH 

14  WATER  FOR  INDUSTRIAL  PURPOSES 

ence  of  a  few  drops  of  methyl  orange  solution  until  a  faint  red  coloration 
(similar  to  that  given  by  methyl  orange  with  a  saturated  solution  of  carbon 
dioxide  in  distilled  water)  is  obtained.  The  result  is  expressed  in  grams 
of  CaCO3  per  litre  of  the  water ;  using  200  c.c.  of  the  water,  each  i  c.c. 
of  the  N/5-HC1  corresponds  with  0-05  gram  of  CaCO3  per  litre. 

When  the  water  contains  sodium  carbonate — which  is  the  case,  not 
with  ordinary  natural  waters,  but  only  with  certain  mineral  waters  and 
with  waters  treated  with  sodium  carbonate — it  is  necessary  to  boil  a  given 
volume  of  the  water  (gradually  replacing  that  which  evaporates)  until 
the  bicarbonates  are  decomposed,  and  then  to  filter  and  determine  the 
alkalimetric  titre  of  the  nitrate.  This  alkalinity  represents  the  sodium 
carbonate  existing  in  the  water,  together  with  those  minute  quantities  of 
the  alkaline  earth  carbonates  which  remain  dissolved  (0-036  gram  of  CaCO3 
and  o-i  gram  of  MgCO3  per  litre).1 

2.  Determination    of    the    Lime    and    Magnesia. — Two    hundred 
c.c.  of  the  water  are  boiled  for  some  minutes  with  excess  of  sodium  carbonate 
solution  in  a  porcelain  dish  and  then  evaporated  to  dry  ness.     The  residue 
is  heated  at  180°  and  treated  with  boiling  water,  the  liquid  being  filtered 
and  the  precipitated  alkaline  earth  carbonates  washed  with  a  little  boiled 
water  and  dissolved  in  excess  of  N/5-hydrochloric  acid.     The  excess  of  acid 
is  then  titrated  with  N/5-caustic  soda  solution  in  presence  of  methyl  orange. 
In  this  case,  lime  and  magnesia  are  calculated  together  as  CaO  ;    when 
200  c.c.  of  the  water  are  taken,  each  c.c.  of  N/5-HC1  used  corresponds  with 
0-028  gram  of  CaO  per  litre  of  the  water.2 

3.  Estimation  of  Sulphates. — To  200  c.c.  of  the  water,  acidified  with 
a  little  hydrochloric  acid,  barium  chloride  is  added  ;    if  an  appreciable 
precipitate  forms  after  some  hours,  the  sulphuric  acid  is  estimated  in  the 
usual  way   (see  Potable  Waters  :    Complete  Analysis,  4).     The  sulphuric 
acid  found  may  be  calculated  as  CaSO4 ;    i    part   of  BaS04  corresponds 
with  0-5827  part  of  CaSO4. 

4.  Other  Tests. — -Where  qualitative  analysis  shows  the  presence  of 
marked  quantities  of  magnesia,  it  is  well  to  determine  this  gravimetrically,  the 
lime  being  first  eliminated  by  means  of  ammonium  oxalate  and  the  mag- 
nesia then  precipitated  with  sodium  phosphate  and  weighed  as  magnesium 
pyrophosphate  in  the  ordinary  way.  1 

When  an  appreciable  amount  of  chlorides  is  indicated  qualitatively,  the 
chlorine  is  determined  (see  Potable  Waters  :  Complete  Analysis,  3)  and 
calculated  as  NaCl. 

Also,  if  qualitative  analysis  reveals  the  presence  of  iron,  this  may  be 
determined  gravimetrically  or  colorimetrically  by  Lunge's  method  (see 
Aluminium  Sulphate). 

5.  Calculation  of  the  Results. — -The  lime  (CaO)  corresponding  with 
the  calcium  sulphate  found  according  to  3  is  subtracted  from  the  total 
lime  found  according  to  2  ;    the  difference  will  represent  the  lime  in  the 

1  The  alkalinity  of  a  water  for  industrial  uses  may  also  be  determined  by  the  method 
indicated  for  Potable  Waters  :    Partial  Analysis,  3. 

2  With  waters  rich  in  magnesia  it  is  convenient  to  follow  the  method  proposed  by 
Wartha  and  Pfeifer  (Zeitschv.  f.  angew.  chem,,  1902,  p.  193)  or  that  of  Gigli  (seep.  5), 


WATER  FOR  INDUSTRIAL  PURPOSES  15 

form  01  carbonate  (56  parts  of  CaO  correspond  with  100  parts  of  CaCO3). 
This  furnishes  a  control  of  the  estimation  of  the  carbonates  according  to  i, 
provided  always  that  the  magnesia  is  small  in  amount ;  where  the  magnesia 
is  not  negligible,  it  must  be  determined  separately,  as  stated  under  4. 

6.  Removal  of  the  Hardness. — To  obtain  an  indication  of  the  quan- 
tities of  lime  and  sodium  carbonate  to  be  added  to  a  water  to  counteract 
excessive  hardness  (see  p.  12),  the  following  tests  may  be  made  : 

Clear  lime  water  is  prepared  and  its  content  of  CaO  established  by  means 
of  N/5-HC1  in  presence  of  phenolphthalein  (i  c.c.  N/5-HC1  =  0-0056 
gram  CaO). 

To  200  c.c.  of  the  water  a  few  drops  of  phenolphthalein  are  added  and 
the  standard  lime  water  run  in  until  a  red  coloration  lasting  for  some 
instants  is  formed.  From  the  number  of  c.c.  of  lime  water  used,  the  amount 
of  lime  (CaO)  necessary  for  i  litre  of  the  water  is  calculated. 

The  turbid  liquid  from  the  preceding  test  is  filtered  and  the  nitrate 
treated  with  a  slight  excess  of  N/5-sodium  carbonate  solution  ;  after  a 
second  nitration,  the  excess  of  sodium  carbonate  in  the  filtrate  is  titrated 
with  N/5-hydrochloric  acid  (indicator  :  methyl  orange).  From  the  differ- 
ence between  the  number  of  c.c.  of  sodium  carbonate  added  and  the  number 
of  c.c.  of  hydrochloric  acid  necessary  to  neutralise  the  excess  of  this 
carbonate,  the  amount  of  sodium  carbonate  which  should  be  added  to  the 
water  (as  well  as  lime  water)  to  decompose  the  calcium  sulphate  may  be 
calculated,  i  c.c.  of  N/5-sodium  carbonate  solution  corresponding  with 
0-0286  gram  of  Na2CO3  +  10  H2O. 

If  it  is  desired  to  eliminate  the  sulphates  by  means  of  barium  chloride, 
i  part  of  SO 3  will  require  3-25  parts  of  commercial,  crystallised  barium 
chloride  (assuming  an  average  of  80%  of  BaCl2). 

* 
*  * 

Water  for  steam  boilers  should  be  clear  and  soft  and  should  not  contain  too 
large  a  proportion  of  substances  which  produce  incrustations  (calcium  and 
magnesium  carbonates,  gypsum,  silica,  aluminium,  iron)  or  corrosion  (chlorides, 
nitrates).  Boiler  water  softened  by  the  above  methods  should  be  only  faintly 
alkaline  (100  c.c.  should  not  require  more  than  1-1-5  c.c.  of  decinormal  acid 
for  neutralisation)  and  its  hardness  should  not  exceed  3-4  degrees,  while  with 
ammonium  oxalate  it  should  turn  only  slightly  milky  after  1-2  minutes. 

Water  for  washing  silk  should  be  of  low  hardness  (this  is  neutralised  with  a 
small  amount  of  acetic  acid)  and  should  contain  no  iron  and  little  organic  matter. 

Water  for  washing  starch  should  be  clear,  with  little  organic  matter  or  fixed 
residue  and  free  from  ammonia,  nitrites,  nitrates  and  iron. 

Water  for  sugar  factories  should  be  pure,  of  low  hardness  and  free  from  alkali 
salts — which  impede  the  crystallisation  of  the  sugar — -and  from  organic  matter 
and  its  decomposition  products  (nitrites,  nitrates  and  ammonia). 

Water  for  brewing  or  distilling  should  be  clear,  odourless,  tasteless  and  neutral  ; 
it  should  have  a  medium  hardness  and  contain  moderate  proportions  of  calcium 
and  magnesium  salts  and  of  sulphates  ;  it  should  contain  little  chloride  or  iron 
and  should  be  as  free  as  possible  from  organic  matter,  nitrites,  nitrates,  ammonia 
and  micro-organisms. 

Water  for  dyeworks  should  exhibit  different  characters  according  to  the  nature 
of  the  dyeing  ;  in  general  it  should  be  very  pure  and  have  very  little  hardness 
and,  especially  for  delicate  colours,  should  not  contain  iron. 


The  products  here  treated  of  are  the  principal  ones  of  the  inorganic  and 
organic  chemical  industries.  Indications  are  given  more  particularly  of 
the  methods  for  their  evaluation  and  for  the  detection  of  the  commoner 
impurities. 

The  name  of  each  product  is  followed  by  the  chemical  formula  and  the 
atomic  or  molecular  weight  referred  to  O  — 16,  according  to  the  inter- 
national atomic  weight  table  for  the  year  1914. 

The  products  are  arranged  alphabetically.  It  must  be  pointed  out  that 
certain  other  chemical  products  are  dealt  with  in  other  chapters  (see  Index 
at  end  of  Vol.  II). 

ACETONE 

C3H60  =  58-05 

Colourless  liquid,  of  peculiar  odour,  miscible  with  water,  D  =  0-7966 
at  15°,  b.pt.  55-56°.  It  may  be  contaminated  with  free  acids,  acetone  oil, 
tarry  matters  and  water,  but  is  usually  very  pure.  The  tests  to  be  made  are 
the  following  : 

1 .  Density  and  boiling  point — by  the  ordinary  methods. 

2.  Acidity. — -Test  with    blue    litmus    paper ;    any    acidity   may   be 
determined  by  titration  with    decinormal    caustic  soda  in  presence    of 
phenolphthalein . 

3.  Fixed  Residue. — 20    grams  are  evaporated  on  a  steam-bath  ;    no 
residue  should  remain. 

4.  Solubility,  Moisture. — Acetone  should  dissolve  in  all  proportions 
in  water  or  in  light  petroleum  boiling  at  40-60°.     Turbidity  with  water 
indicates  the  presence  of  acetone  oil  or  tarry  matter.     If  drops  of  water 
separate  at  the  bottom  when  the  acetone  is  mixed  with  light  petroleum, 
water  is  present. 

5.  Tarry  Matters.— 5  c.c.  of  the  acetone  are  treated  with  a  drop  of 
0-1%  potassium  permanganate  solution  ;  the  liquid  should  remain  red  for 
at  least  15  minutes  if  the  acetone  is  pure. 

6.  Aldehydes.— 10  c.c.  of  the  acetone  are  treated  with  10  c.c.  of  dis- 
tilled water  and  2  c.c.  of  ammoniacal  silver  nitrate  solution  (3  grams  AgNO3, 
3  grams  NaOH  and  20  grams  of  ammonia  solution  of  D  =  0-9,  made  up  to 
100  c.c.  with  water)  and  left  for  15  minutes  in  the  dark.     If  there  is  reduc- 
tion, the  filtered  liquid  is  tested  with  ammonium  sulphide  ;  if  a  precipitate 
is  formed,  the  proportion  of  aldehyde  does  not  exceed  o-i.% 

16 


ACETONE  OILS  17 

7.  Quantitative  Determination. — Messinger's  method  is  used  (see 
Methyl  Alcohol). 

Commercial  pure  acetone  should  be  colourless  and  neutral,  of  D  not  exceeding 
o'-8oo  at  15°,  should  distil  to  the  extent  of  at  least  95%  below  58°,  and  should 
mix  in  all  proportions  with  water.  It  should  leave  no  residue  on  evaporation, 
should  not  decolorise  permanganate,  and  should  not  contain  more  than  0-1% 
of  aldehydes. 


ACETONE   OILS 

These  residues  from  the  purification  and  rectification  of  crude  acetone 
consist  mainly  of  various  higher  ketones  (methyl  ethyl  ketone,  methyl 
propyl  ketone)  and  form  more  or  less  intensely  yellow  liquids  of  peculiar 
and  disgusting  odour,  acrid,  burning  taste,  D  0-828-0 -842,  b.pt.  very  variable 
according  to  the  quality  (75°  to  110°  or  even  higher)  ;  they  are  only  partly 
soluble  in  water  but  are  miscible  in  all  proportions  with  alcohol.  The 
tests  made  include  distillation,  solubility  in  water,  acetone  content  and 
bromine  absorption. 

1.  Distillation. — A  100  c.c.  flask,  identical  with  that  used  for  the 
distillation  of  pyridine  bases  (see  chapter  on  Tar  and  its  Products),  is  used, 
the  distillation  being  arranged  so  that  the  liquid  passes  over  drop  by  drop  ; 
the  different  fractions  corresponding  with  each  5°C.  are  collected  in  graduated 
cylinders  or  tubes. 

2.  Solubility  in  Water. — In  a  100  c.c.  graduated  cylinder  are  placed 
20  c.c.  of  the  oil  and  20  c.c.  of  water.     After  vigorous  shaking,  the  liquid 
is  allowed  to  stand  until  two  distinct  layers  are  formed,  the  number  of  c.c. 
of  oil  dissolved  being  noted.     Sixty  c.c.  of  water  are  then  added  and  the 
volume  of  oil  dissolved  determined  as  before.    The  results  obtained  are 
multiplied  by  5  and  expressed  thus  : 

(a)  Solubility  in  an  equal  volume  of  water  :  .  .  .  c.c.  per  100  of  the  oil. 

(b)  Solubility  in  four  volumes  of  water  :  .  .  .  c.c.  per  100  of  the  oil. 

3.  Ketone  Content. — In  this  determination,  the  same  liquids  are  used 
as  in  the  determination  of  acetone  in  crude  methyl  alcohol,  and  the  same 
procedure   is   followed  (see   Methyl  Alcohol,  Determination  of  Acetone). 
Ten  c.c.  of  the  oil  are  made  up  to  1000  c.c.  with  water  in  a  graduated  flask, 
which  is  shaken  so  as  to  extract  the  soluble  part  of  the  oil  as  far  as  possible. 
Ten  c.c.  of  the  liquid  (corresponding  with  o-i  c.c.  of  the  oil)  are  placed  in  a 
bottle  holding  300-400  c.c.  and  provided  with  a  ground  stopper ;    20  c.c. 
of  solution  a  are  then  added  and  50  c.c.  of  solution  c  run  in  gradually  from  a 
burette.     The  bottle  is  tightly  stoppered,  well  shaken  and  then  left  for  an 
hour  with  occasional  agitation.     Twenty  c.c.  of  solution  b  are  next  added 
and  the  liquid  titrated  with  thiosulphate  solution  d  in  presence  of  starch 
paste. 

Thus,  by  difference,  the  quantity  of  iodine,  a,  absorbed  by  the  oil  is 
obtained,  the  formula, 

x  =^,?-^-X  1000, 
761-52 

giving  the  weight  of  ketones,  expressed  as  methyl  ethyl  ketone,  in  100  c.c. 
A.C.  2 


i8  ACETIC  ACID 

The  percentage  by  volume  is  found  by  dividing  this  result  by  the  average 
density  of  acetone  oil,  namely,  0-840. 

4.  Absorption  of  Bromine. — This  is  carried  out  as  with  crude  methyl 
alcohol  (q.v.). 

* 
*   * 

Acetone  oils  vary  in  composition  with  the  quality  of  the  calcium  pyrolignite 
from  which  they  are  obtained,  and  with  the  conditions  of  the  distillation,  etc. 

Light  acetone  oils  are  yellowish  liquids  of  repulsive  odour  and  burning,  acrid 
taste.  They  boil  in  general  between  70°  and  100°  (mostly  at  70-80°),  are  soluble 
to  the  extent  of  40-50%  in  an  equal  volume  of  water  and  to  the  extent  of  90-95  % 
in  four  volumes  of  water,  and  contain  90-95%  by  volume  of  ketones  calculated 
as  methyl  ethyl  ketone.  Light  acetone  oils  are  used  especially  for  the  denatura- 
tion  of  alcohol  and  in  different  countries  have  to  satisfy  definite  conditions  as 
regards  colour,  density,  boiling  point,  solubility  in  water,  content  of  ketones,  etc. 

Heavy  acetone  oils  have  a  more  pronounced  yellow  colour  than  the  light 
oils,  are  less  soluble  in  water,  and  boil  at  130-250°. 

ACETIC    ACID 

C2H4O2  =  60-03  (60) 

Various  qualities  are  found  on  the  market  :  Crude  pyroligneous  acid, 
brown,  turbid  liquid  with  a  strong  empyreumatic  odour,  D  about  1-013, 
containing  5-10%  of  acetic  acid.  Commercial  acetic  acid,  colourless  or 
yellowish  liquid  with  more  or  less  marked  empyreumatic  odour  ;  it  may 
contain  90-95%  of  acetic  acid  or  may  be  more  dilute  (30-60%),  the  principal 
impurity  being  hydrochloric,  sulphuric  or  sulphurous  acid.  The  pure  or 
puriss.  glacial  acid  is  colourless,  has  a  pure  acetic  odour  and  contains  96— 
100%  of  the  acid  (D  1-0644-1 -0553),  the  usual  content  being  96—98%  (D 
1-0644-1-0604)  ;  it  boils  at  about  118°  and  at  about  +  10°  solidifies  to 
colourless,  transparent,  lamellar  crystals. 

Analysis  of  acetic  acids,  which  may  be  contaminated  with  salts  of  copper, 
lead,  iron  and  calcium  and  with  arsenic,  hydrochloric,  sulphuric  and  sul- 
phurous acids,  and  organic  and  pyrogenic  substances,  comprises  mainly 
the  following  determinations  and  tests  : 

1.  Specific  Gravity. — This  is  measured  in  the  ordinary  manner  (hydro- 
meter, Mohr's  balance).     In  the  case  of  a  pure  acid,  the  content  of  acid 
may  be  determined  from  the  specific  gravity  by  means  of  Oudemans'  table, 
which  is  given  in  the  various  books  of  chemical  tables. 

2.  Residue  on  Evaporation. — 10  c.c.  are  evaporated  by  gentle  heating 
in  a  dish  to  ascertain  if  any  carbonaceous  residue  (organic  matters)  remains  ; 
this  is  then  calcined,  a  solid  residue  showing  the  presence  of  mineral  sub- 
stances. 

3.  Metals. — 1-2  c.c.,  diluted  with  20  c.c.  of  water,  should  not  be  ren- 
dered turbid  by  hydrogen  sulphide  (copper,  lead],  or  by  excess  of  ammonia 
and  ammonium  sulphide  (iron)  or  by  ammonium  oxalate  (calcium). 

4.  Arsenic. — 1-2  c.c.,  treated  with  5  c.c.  of  Bettendorf's  reagent,^  should 
give  no  coloration  within  an  hour. 

1  Bettendorf's  reagent  is  prepared  by  dissolving  20  parts  of  pure  tin  in  65  parts  of 
pure  concentrated  hydrochloric  acid  at  a  gentle  heat,  replacing  the  water  evaporated, 
and  saturating  with  dry,  gaseous  hydrogen  chloride. 


BORIC  ACID  19 

5.  Sulphuric  and  Hydrochloric  Acids. — Separate  portions  of  1-2 
c.c.,  diluted  with  20  c.c.  of  water,  should  not  be  rendered  turbid,  even  after 
some  hours,  by  barium  chloride  or  by  silver  nitrate  and  nitric  acid. 

6.  Sulphurous  Acid. — After  treatment  with  barium  chloride  to  test 
for  sulphuric  acid,  the  liquid  is  filtered  if  necessary  and  the  nitrate  oxidised 
with  chlorine  or  bromine  water  ;   the   formation  of  a  turbidity   indicates 
the  presence  of  sulphurous  acid,  which  is  oxidised  to  sulphuric  acid  and 
thus  precipitated  by  the  excess  of  barium  chloride. 

7.  Empyreumatic  Substances. — These  are  readily  detected  by  the 
smell  and  taste.     Small  proportions  are  tested  for  by  diluting  5  c.c.  of  the 
acid  with  15  c.c.  of  water  and  adding  I  c.c.  of  0-1%  permanganate  solution  : 
the  red  colour  should  persist  for  10  minutes  at  least. 

8.  Estimation  of  the  Acetic  Acid. — In  absence  of  other  acids  titration 
suffices,  a  few  grams  of  the  acid  being  diluted  with  water  and  titrated  with 
normal  potash  or  soda  in  presence  of  phenolphthalein  ;    i  c.c.  N-alkali  = 
0-060  gram  of  acetic  acid.     When  the  acid  contains  free  sulphuric  and 
hydrochloric  acids,  these  must  be  estimated  separately  by  the  ordinary 
methods. 

With  acetic  acid  containing  large  proportions  of  empyreumatic  sub- 
stances, Scheurer-Kestnei  's  method  *  is  employed :  20  grams  of  the  acid 
and  50  grams  of  phosphoric  acid  (15°  Baume)  are  distilled  slowly  from  a 
glass  retort.  When  about  one-half  of  the  liquid  has  distilled  over,  25  c.c. 
of  water  are  added  to  the  retort  and  the  distillation  continued  until  a  drop 
of  the  distillate  fails  to  redden  blue  litmus  paper.  The  acetic  acid  in  the 
distillate  is  then  determined  by  means  of  normal  soda  and  phenolphthalein. 

BORIC    ACID 

H3BO3  =  62-02  (62) 

This  is  sold  in  white  scales  (yellowish  or  brownish  if  the  product  is 
crude)  or  in  a  crystalline  powder.  It  dissolves  in  about  25  parts  of  cold 
or  3  of  boiling  water,  and  also  in  alcohol  or  glycerine. 

It  may  contain  sulphates,  alkali  chlorides,  ammonium  salts,  ferric 
oxide,  alumina,  lime,  magnesia,  silica  and  organic  substances. 

1.  Insoluble   Substances. — 2-3  grams  are  dissolved  in  hot  water, 
the  insoluble  matter  being  collected  on  a  tared  filter,  washed,  dried  and 
weighed. 

2.  Silica,   Chlorides,    Sulphates. — The  nitrate  from  the  preceding 
operation  is  acidified  with  nitric  acid  ;  one  part  of  the  liquid  is  evaporated 
to  dryness  for  the  detection  of  silica,  and  others  treated  with  silver  nitrate 
and  barium  chloride  respectively  to  detect  chlorides  and  sulphates.    With 
measured  volumes  of  solution,  these  tests  may  be  made  quantitative. 

3.  Alumina,    Iron,    Lime,    Magnesia,    Alkalies. — 2-3   grams    are 
evaporated  to  dryness  with  excess  of  pure  sulphuric  and  hydrofluoric  acids 
in  a  platinum  dish,  the  boric  acid  being  thus  completely  eliminated  as 
boron  fluoride.     The  residue  is  treated  with  dilute  hydrochloric  acid  and 
the  solution  used  for  the  detection  or,  if  necessary,  the  estimation  of  the 
iron,  alumina,  lime,  magnesia  and  alkalies. 

1  Butt.  Soc.  fhim,  de  Paris,  1896,  XV,  p.  530. 


20  CARBONIC  ACID 

4.  Ammonia. — This  is  estimated  by  distilling  with  excess  of  caustic 
soda  (see  Fertilisers). 

5.  Determination  of  the  Boric  Acid. — This  is  readily  effected  by 
Jorgensen's  modification  of  Honig  and  Spitz's  volumetric  method  :     10 
grams  of  the  acid  are  dissolved  in  500  c.c.  of  recently  boiled  water  and  to 
50  c.c.  of  the  solution  (i  gram  of  substance)  are  added  50  c.c.  of  pure  glycerine 
(previously  neutralised  with  caustic  soda  if  the  reaction  is  acid)  and  a  few 
drops  of  phenolphthalein.     The  liquid  is  then  titrated  with  N/2-sodium  or 
barium  hydroxide   (absolutely  free  from  carbonates)  until  a  red  coloration 
is  just  reached  ;    a  further  10  c.c.  of  the  glycerine  are  added  and,  if  the 
colour  disappears,  the  titration  is  continued,  this  process  being  repeated 
until  addition  of  glycerine  no  longer  destroys  the  red  colour.     This  is  the 
case  when  i  mol.  of  H3BO3  is  combined  with  i  mol.  of  NaOH  ;    i  c.c.  of 
N/2-alkali  =  0-031  gram  of  H3BO3. 

Commercial  crude  boric  acid  contains  80-95%  H3BO3  and  the  refined  product 
not  less  than  99%. 

CARBONIC    ACID 

CO2  =  44 

This  is  sold  in  the  liquefied  condition,  compressed  in  steel  cylinders  of 
various  capacities.  It  may  contain  air,  carbonic  oxide,  mineral  acids, 
empyreumatic  substances  and  various  mechanical  impurities  (especially 
lubricating  oils) ,  which  collect  at  the  botl  om  of  the  vessel  as  a  thick,  brown 
liquid  of  repulsive  odour.  Analysis  comprises  the  following  : 

1.  Gaseous   Impurities. — The  gas  is  introduced  into  a  graduated 
cylinder  over  mercury  x  and  there  left  in  contact  with  a  few  c.c.  of  boiled, 
concentrated  caustic  soda  solution  ;  the  residual  unabsorbed  gas  represents 
the  gaseous  impurities  of  the  carbonic  acid.     According  to  Werder,2  the 
carbonic  acid  may  be  passed  through  an  Orsat  apparatus  with  three  absorp- 
tion bulbs,  the  first  containing  potassium  hydroxide  solution  to  absorb  the 
carbon  dioxide,  the  second  potassium  pyrogallate  solution  to  absorb  the 
oxygen  and  the  third  ammoniacaf~cuprous  chloride  solution  for  the  carbon 
monoxide. 

2.  Empyreumalic    Substances. — -A   current   of   the   gas   is   passed 
through  concentrated  sulphuric  acid  ;  if  the  gas  is  impure,  the  acid  becomes 
brown. 

3.  Sulphurous  and  Nitrous  Acids. — If  either  of  these  is  present, 
passage  of  the  gas  through  potassium  permanganate  solution  gradually 
decolorises  the  latter. 

4.  Hydrochloric   Acid. — When  this  is  present,  passage  of  the  gas 
through  a  dilute  silver  nitrate  solution  acidified  with  nitric  acid  renders 
the  liquid  turbid. 

As  a  rule  the  acid  of  commerce  is  moderately  pure  and  contains  only  small 
proportions  of  air  (up  to  6%),  and  rarely  carbon  monoxide  (up  to  4%).  A  good 
carbonic  acid  should  contain  at  least  98%  by  volume  of  CO2  and  not  more  than 
0-5%  of  CO,  and  should  be  free  from  mineral  acids  and  empyreumatic  substances. 

1  Instead  of  a  cylinder  over  mercury,  a  Winkler  burette  or  any  other  form  of  gas- 
measuring  apparatus  may  be  used. 

2  Chem.  Zeit.,  1906,  p.   1021. 


CITRIC  ACID  21 

CHROMIC    ACID 

CrO3  =  100 

Pure  chromic  acid  forms  dark  ruby-red,  silky,  acicular  crystals,  but 
that  used  technically  is  in  much  smaller  crystals  or  in  red  crystalline  masses. 
The  impurities  present  are  mainly  sulphuiic  acid  and  alkali  salts,  more 
rarely  nitric  acid  and  barium  and  lead  salts. 

1.  Sulphuric  Acid.— i  gram  in  20  c.c.  of  water  should  give  a  clear 
solution,  which  is  not  rendered  turbid  by  addition  of  hydrochloric  acid 
and  barium  chloride. 

2.  Alkali  Salts. — o-i  gram  is  heated  to  redness  and  the  residue  treated 
with  water  and  filtered  ;   if  the  filtrate  is  yeUow,  alkali  salts  are  present. 

3.  Nitric  Acid. — I  gram  is  dissolved  in  water  and  the  liquid  treated 
with  sulphurous  acid  solution  until  it  becomes  distinctly  green  and  then 
with  ammonia  ;    the  liquid  is  boiled  and  filtered,  and  the  filtrate  (which 
should  be  colourless)  tested  for  nitric  acid  in  the  usual  way. 

4.  Barium  or  Lead  Salts. — A  few  grams  are  treated  with  water  and 
a  few  drops  of  dilute  sulphuric  acid ;    after  standing,  the  clear  liquid  is 
decanted  and  any  residue  examined  for  lead  or  barium  sulphate. 

5.  Determination  of  the  Chromic  Acid. — About  O'i  gram  is  boiled 
with  hydrochloric  acid  and  the  liberated  chlorine  collected  in  potassium 
iodide  solution.     The  iodine  set  free  by  the  chlorine  is  then  estimated  by 
means  of  sodium  thiosulphate  solution  and  starch  paste  (i  c.c.  of  N-thio- 
sulphate  =  0-03339  gram  CrO3). 

Even  "  pure  "  chromic  acid  generally  contains  small  proportions  of  sulphuric 
acid  or  sulphates.  In  the  commercial  product  as  much  as  30%  of  potassium 
sulphate  has  been  found  (Krauch). 

CITRIC    ACID 

C6H807  +  H2O  =  210 

Large,  colourless,  odourless,  non-hygroscopic  crystals  of  acid  taste, 
soluble  in  water  and  alcohol  and,  to  a  less  extent,  in  ether.  They  may 
contain  tartaric,  oxalic  and  sulphuric  acids  and  salts  of  calcium,  iron  and 
heavy  metals  (especially  lead  and  copper). 

1.  Tartaric  Acid. — i  gram  of  the  acid  is  dissolved  in  2  c.c.  of  water 
and  the  solution  treated  with  potassium  acetate  and  alcohol :  no  turbidity 
should  be  produced.     Very  small  amounts  may  be  detected  by  dissolving 
i  gram  of  the  acid  in  10  c.c.  of  distilled  water  and  gradually  pouring  part 
of  the  solution  into  15-20  c.c.  of  lime  water,  which  should  remain  clear. 

2.  Oxalic  Acid. — i  gram  of  the  acid,  dissolved  in  10  c.c.  of  water, 
should  not  be  rendered  turbid  by  addition  of  calcium  sulphate  solution. 

3.  Sulphuric  Acid  and   Sulphates. — The  aqueous  solution   (i :  10) 
should  not  be  rendered  turbid  by  addition  of  barium  chloride  and  hydro- 
chloric acid. 

4.  Lime. — The  aqueous  solution   (i  :  10),  neutralised  with  ammonia, 
should  not  be  rendered  turbid  by  addition  of  ammonium  oxalate. 

5.  Ash. — 10  grams  of  the  acid  are  carefully  burned  in  a  crucible  and 


22  CITRIC  ACID 

the  ash  weighed.     If  this  exceeds  0-5%,  a  greater  quantity  of  the  acid  is 
burned  and  the  ash  tested  for  lead,  copper  and  iron. 

6.  Lead. — Of  particular  importance  is  the  determination  of  the  lead, 
the  presence  of  which  in  small  quantities  is  due  to  the  crystallisation  vessel. 
Warington's  colorimetric  method  is  used  : 

A  standard  lead  solution  is  prepared  by  dissolving  about  50  grams  of 
ammonium  citrate  (puriss.)  and  O'Oi6  gram  of  lead  nitrate  (corresponding 
with  o«oi  gram  Pb)  in  water  and  making  up  to  500  c.c.  From  this  a  scale 
of  tints  is  prepared  by  diluting  varying  volumes  of  the  liquid  (e.g.,  I,  2,  3, 
5,  10,  15,  20  c.c.,  etc.)  to  50  c.c.  and  adding  to  each  a  drop  of  ammonium 
sulphide. 

Forty  grams  of  the  citric  acid  are  dissolved  in  water  and  slight  excess 
of  ammonia  added,  the  cooled  liquid  being  diluted  to  500  c.c.  To  50  c.c. 
of  this  solution  is  added  a  drop  of  ammonium  sulphide,  the  coloured  liquid 
thus  obtained  being  compared  with  the  above  colour  scale.  The  judging  of 
the  colours  is  aided  by  addition  of  a  little  glycerine,  which  renders  the 
colours  sharper  and  prevents  the  formation  of  precipitate.  In  this  way 
the  lead  content  of  citric  acid  may  be  determined  with  great  accuracy. 

7.  Determination  of  the  Citric  Acid. — In  absence  of  other  acids,  it 
suffices  to  dissolve  1-2  grams  of  the  acid  in  water  and  to  titrate  the  solution 
with  normal  potassium  hydroxide  solution  in  presence  of  phenolphthalein ; 
i  c.c.  of  N-alkali  =  0-07  gram  of  crystallised  citric  acid  (C6H8O7  +  H2O) 
and  14-5  c.c.  of  N-alkali  =  I  gram  of  the  crystallised  acid. 

In  presence  of  other  acids,  usually  oxalic  and  tartaric,  these  extraneous 
acids  must  be  separated  and,  if  necessary,  estimated  : 

(a)  PRESENCE  OF  OXALIC  ACID. — 2-3  grams  of  the  citric  acid,  are  dis- 
solved in  water  and  neutralised  with  caustic  soda  ;   the  liquid  is  acidified 
with  acetic  acid  and  a  solution  of  calcium  sulphate  or  chloride  added.     The 
calcium  oxalate  formed  is  filtered  off,  washed  with  hot  water  and  weighed 
as  carbonate  or  oxide.     In  the  filtrate  the  citric  acid  is  determined  by  pre- 
cipitation as  indicated  under  analysis  of  lemon  juice  (see  later,  4).     Where 
determination  of  the  oxalic  acid  is  unnecessary,  this  precipitation  method 
is  applied  directly  to  2  grams  of  the  acid. 

(b)  PRESENCE  OF  TARTARIC  ACID  (Allen's  method). — 2  grams  of  the 
citric  acid  are  dissolved  in  20  c.c.  of  57%  alcohol,  the  liquid  being  filtered 
if  necessary  and  made  up  to  45  c.c.  with  alcohol  of  the  same  strength  ;    5 
c.c.  of  a  cold,  saturated  solution  of  potassium  acetate  in  57%  alcohol  are 
then  added  and  the  liquid  shaken  for  10  minutes.     The  presence  of  tartaric 
acid  leads  to  the  formation  of  insoluble  acid  potassium  tartrate,  which  may 
be  collected  on  a  filter,  washed  first  with  cold  saturated  potassium  bitar- 
trate  solution  and  then  with  57%  alcohol,  dried  at  100°  and  weighed.     The 
weight,  multiplied  by  0-8,  or  the  number  of  c.c.  of  normal  alkali  used  for 
its   titration,    multiplied   by   0-150,    gives   the   amount   of   tartaric   acid 
contained  in  the  2  grams  of  substance  taken.     In  the  filtrate  from  the 
bitartrate  the  citric  acid  is  determined  as  in  lemon  juice. 

•** 

Citric  acid  should  dissolve  completely  in  water  or  alcohol  without  leaving 


CITRIC  ACID  23 

any  trace  of  calcium  sulphate.  Its  crystals  should  not  be  deliquescent  owing 
to  the  presence  of  traces  of  sulphuric  acid.  It  may  give  0-05-0-25%  of  ash  ; 
it  is  always  necessary  to  test  for  copper  and  lead,  and  to  determine  the  latter. 
The  presence  of  these  poisonous  metals  is  accidental,  and  as  a  rule  they  do  not 
exceed  0-01%  in  commercial  citric  acid.  The  proportion  of  lead  varies  some- 
what ;  samples  of  English  origin  have  shown  from  0-0018  to  0-024%,  French 
and  German  samples  from  0-0006  to  0-0029%,  and  American  samples  from  0-003 
to  0-0063%.  According  to  some  authorities  the  maximum  limit  allowable 
should  be  0-002%  of  lead,  whilst  others  give  0-5  m.  grm.  per  100  grams.  Not 
infrequently  commercial  citric  acid  is  adulterated  with  tartaric  acid. 

Lemon  Juice,  etc. 

The  juice  pressed  from  lemons  contains  citric  acid  and  is  used  mainly 
for  the  preparation  of  calcium  citrate  and  thus  of  citric  acid.  The  crude 
juice  (agro  crudo]  is  a  greenish-yellow  liquid  with  an  acid  taste  resembling 
that  of  the  lemon  in  the  fresh  juice  ;  later  the  taste  becomes  bitter.  The 
concentrated  juice  (agro  cotto]  is  a  dense,  syrupy,  brown  liquid  with  an 
odour  recalling  that  of  caramel  and  a  bitter,  highly  acid  flavour. 

The  bergamot  and  wild  lemon  (Citrus  limetta]  also  give  crude  and  con- 
centrated juice,  which  differ  somewhat  in  objective  properties  from  that 
of  the  lemon  ;  berga-mot  juice,  prepared  specially  in  Calabria,  is  also  used 
for  making  calcium  citrate. 

Analysis  of  the  juice  includes  determinations  of  the  specific  gravity, 
free  acidity,  citric  acid  and  other  organic  acids  united  with  bases,  true 
citric  acid,  alcohol  and  adulterants,  these  being  usually  free  mineral  acids 
or  salt  water. 

1.  Specific  Gravity. — This  is  measured  with  a  hydrometer  or  a  Mohr's 
balance.     Use  is  also  made  of  a  citrometer,  which  is  a  hydrometer  on  which 
60  degrees  corresponds  with  the  specific  gravity  1-24,  this  being  a  standard 
for  concentrated  juice. 

2.  Free  Acid. — 50  c.c.  of  the  concentrated  juice  are  diluted  to  500  c.c. 
with  water  and  25  c.c.  (—2-5  c.c.  of  juice),  then  titrated  with  N/2-soda, 
using  neutral  litmus  paper  as  indicator.     With  the  non-concentrated  juice, 
10  or  20  c.c.  are  taken  directly.     In  any  case,  before  complete  neutralisation, 
when  about  five-sixths  of  the  free  acidity  has  been  neutralised,  the  liquid 
is  boiled  for  a  few  minutes  and  the  titration  then  concluded.     The  acidity 
is  calculated  as  crystallised  citric  acid ;    i  c.c.  N/2-alkali  =  0-035  gram 
of  C6H,,O7  +  H2O.     To  give    the  result  in  ounces  per  gallon,  after  the 
English  way,  the  percentage  found  is  multiplied  by  1-60. 

3.  Citric  and  other  Organic  Acids  combined  with  Bases. — The 
neutral  solution  remaining  from  the  preceding  determination  is  evaporated 
to  dryness  and  the  residue,  after  cautious  incineration,  treated  with  water 
and  with  a  measured  volume  of  N-sulphuric  acid  ;  after  boiling  and  filtering, 
the  excess  of  sulphuric  acid  in  the  filtrate  is  determined  by  titration  with 
N-alkali.    The  amount  of  sulphuric  acid  used  to  neutralise  the  ash  is  equiva- 
lent to  the  total  organic  acids  in  the  substance,  since  all  the  organic  salts 
are  transformed  into  carbonates  on  incineration.     Hence,  if  the  total  acids 
are  calculated  as  citric  acid  (i  c.c.  of  N-sulphuric  acid  —  0*070  gram  of 
crystalline  citric  acid,  C6H8O7  +  H2O)  and  from  this  is  deducted  the  free 


24  CITRIC  ACID 

citric  acid  found  in  the  preceding  determination,  the  result  is  the  combined 
citric  acid  (and  other  acids). 

4.  True  Citric  Acid. — From  15  to  20  c.c.  of  non-concentrated  or  about 
3  c.c.  of  concentrated  juice  are  weighed  out  and  neutralised  exactly  with 
approximately   2N-caustic  soda  solution.      The  liquid  is  diluted  to  about 
50  c.c.  and  20  c.c.  of  about  40%  pure  calcium  chloride  solution  added  ;  the 
whole  is  then  acidified  with  a  few  drops  (4-6)  of  seminoimal  hydrochloric 
acid,  the  subsequent  procedure  being  exactly  as  described  for  the  deter- 
mination of  citric  acid  in  calcium  citrate  (see  Calcium  Citrate,  6,  second 
paragraph). 

5.  Alcohol. — Any  alcohol  present  in  the  juice  is  determined  by  dis- 
tillation in  the  usual  way  (see  Wines,  Vol.  II). 

6.  Sulphuric,   Hydrochloric   and   Nitric   Acids. — These  acids  and 
their  salts  are  tested  for  by  the  ordinary  reagents  or  by  the  tests  given  for 
free  mineral  acids  in  vinegar  (see  Vinegar,  Vol.  II).     According  to  Scribani,1 
nitric  acid  is  easily  detected  by  adding  to  the  juice  (diluted  if  too  highly 
coloured)  a  little  hydrochloric  acid  solution  of  ferrous  chloride  free  from 
ferric  salt,  boiling  and  then  adding  potassium  thiocyanate  solution  ;    if 
nitric  acid  is  present  in  the  juice,  a  red  coloration  is  formed  owing  to  oxida- 
tion of  the  ferrous  salt. 

7.  Sulphurous   Acids,   Sulphites. — The  clear,  more  or  less  yellow 
juices  intended  for  the  preparation  of  syrups  and  beverages  may  contain 
sulphurous  anhydride  added  as  preservative. 

(a)  Qualitative  Test.     50-100  c.c.  of  the  juice  are  introduced  into  a 
flask  which  is  closed  by  a  cork  slit  at  the  bottom  to  allow  of  the  insertion 
of  a  freshly  prepared  starch-iodide  paper  z  moistened  at  the  extremity  ;  if 
thejlask  is  heated  gently,  the  paper  will  assume  a  blue  or  brown  colour  if 
sulphurous  acid  or  a  sulphite  is  present. 

(b)  Quantitative  Determination. — From  50  to  100  c.c.  of  the  juice  mixed 
with  5  c.c.  of  20%  phosphoric  acid  are  distilled  in  a  current  of  carbon  dioxide. 
From  25  to  50  c.c.  of  distillate  are  collected  in  50  c.c.  of  N/io-iodine  solution 
contained  in  a  flask  with  a  doubly-bored  stopper,  through  which  pass  the 
condensing  tube  and  a  second    tube  leading  to  a  U-tube  charged  with  a 
definite  volume  of  N/5o-sodium  thiosulphate  solution  (say,  10  c.c.).     At 
the  end  of  the  distillation,  the  contents  of  this  tube  are  washed  into  the 
iodine  solution  and  the  excess  of  iodine  titrated  with  the  sodium  thiosulphate. 

The  number  of  c.c.  of  iodine  solution  used  up  in  oxidising  the  sulphurous 
acid,  multiplied  by  0-00064,  gives  the  quantity  of  sulphur  dioxide  in  the 
juice. 

The  sulphur  dioxide  may  also  be  determined  gravi metrically  on  the 
distilled  product  collected  in  the  iodine  solution  (see  Beer,  Vol.  II). 

* 
*  * 

Besides  free  citric  acid,  which  represents  88-98%  of  the  total  acidity,  lemon 
juice,  etc.,  contains  small  proportions  of  citrates,  other  free  organic  acids  and 

1  Gazzetta  chimica  italiana,  1878,  VIII,  p.  234. 

2  The  solution  for  the  preparation  of  this  paper  is  made  from  o  •  i  gram  of  potassium 
iodide  and  i  gram  of  starch  in  100  c.c.  of  distilled  water. 


FORMIC  ACID  25 

their  salts,  iron,  mineral  salts,  saccharine  substances,  albuminoids,  gummy 
matters,  etc.,  and  sometimes  alcohol  (up  to  1-5%  by  volume).  Concentrated 
lemon  juice  contains  about  40%  of  citric  acid  and  has  the  density  1-2-1-4.  The 
crude  juice  has  the  density  1-03-1-04  and  contains  variable  proportions  of  citric 
acid  (4-7%).  The  crude  and  concentrated  juices  from  the  bergamot  contain 
less  citric  acid  than  lemon  juice  (about  30%  in  the  concentrated  juice). 

These  juices  may  be  adulterated  with  salt,  which  increases  the  density,  or 
with  sulphuric,  tartaric  or  nitric  acid,  which  increases  the  acidity.  The  pure 
juices  should  contain  only  traces  of  sulphates  and  chlorides. 

These  juices  are  usually  quoted  in  English  measures,  the  unit  of  volume  being 
taken  as  the  pipe  of  108  imperial  gallons  (i  gallon  =  4-536  litres)  and  that  of 
weight  as  the  ounce  (28-35  grams).  The  crude  juice  is  quoted  on  the  basis  of 
ii  ozs.  of  citric  acid  per  gallon,  and  the  concentrated  juice  on  the  basis  of  66-87 
ozs.  of  free  crystallised  citric  acid  (C6H8O7,  H2O)  or  64  ozs.  of  the  acid,  C6H8O7, 
J  H2O.  Bergamot  juice  is  generally  quoted  on  the  basis  of  48  ozs.  per  gallon. 

FORMIC    ACID 

H2CO2  =  46 

In  the  pure  state  this  is  a  colourless  liquid  of  particularly  pungent  odour, 
D  =  I-225-I-227  (at  15°),  b.pt.  100° ;  it  is  extremely  soluble  in  water 
and  at  o°  solidifies  to  crystals  which  melt  again  at  about  8°.  It  is  placed 
on  the  market  in  various  concentrations,  up  to  almost  100%,  but  usually 
85%  (D  =  1-202). 

It  may  contain  mineral  acids  (especially  hydrochloric  acid),  acetic  acid 
(mixtures  of  formic  acid  with  varying  proportions  of  acetic  acid  are  sold 
as  acetargol),  oxalic  acid,  salts  of  the  alkalies  and  heavy  metals  (lead,  copper, 
iron),  arsenic  (occasional  traces),  acrolein,  allyl  alcohol  and  empyreumatic 
substances.  The  following  tests  are  made. 

1.  Mineral  Acids. — 10  c.c.  of  the  acid  are  diluted  with  100  c.c.  of 
water,  50  c.c.  being  then  treated  with  silver  nitrate  (in  the  cold)  and  50  c.c. 
with  barium  chloride. 

2.  Acetic  Acid. — 1-2  c.c.  of  the  acid,  diluted  with  20  c.c.  of  water 
and  mixed  with  6rgrams  of  yellow  mercuric  oxide,  are  heated  on  the  water- 
bath  until  evolution  of  gas  (CO2)  ceases  and  the  liquid  then  filtered.     In 
the  case  of  pure  formic  acid,  the  filtrate  has  a  neutral  reaction  (all  the  formic 
acid  being  decomposed),  but  in  presence  of  acetic  acid  the  filtrate  is  acid 
and  permits  of  the  identification  of  the  acetic  acid  by  the  odour. 

The  quantitative  determination  of  acetic  acid  when  mixed  with  formic 
acid  may  be  effected  by  Hamel's  method  :  3-4  grams  of  the  acid  are  neu- 
tralised with  N-sodium  hydroxide  (towards  phenolphthalein),  the  liquid 
evaporated  to  dryness  on  a  water-bath  and  the  residue  dried  in  an  oven  at 
120-130°  and  weighed.  It  is  then  treated  with  excess  of  pure  formic  acid 
(which  liberates  acetic  acid  from  its  salts),  again  evaporated  to  dryness, 
the  residue  "being  then  taken  up  in  a  little  water,  once  more  evaporated 
and  the  residue  dried  at  120-130°  and  weighed.  From  the  difference 
between  the  two  weights  the  acetic  acid  is  calculated. 

3.  Oxalic  Acid. — 2  c.c.  of  the  acid  are  diluted  with  20  c.c.  of  water 
and  the  liquid  rendered  alkaline  with  ammonia  and  treated  with  calcium 
chloride  ;    a  turbidity  indicates  oxalic  acid. 

4.  Various  Mineral  Salts. — 10  c.c.  of  the  acid,  evaporated  on  a  steam- 


26 

bath,  should  leave  no  appreciable  residue,  and  2  c.c.,  diluted  with  20  c.c. 
of  water  and  rendered  alkaline  with  ammonia,  should  undergo  no  change 
with  ammonium  sulphide. 

5.  Acrolein,     Allyl     Alcohol,     Empyreumatic    Products. — These 
are  recognised  by  the  odour,  after  neutralisation  of  the  acid  with  sodium 
hydroxide. 

6.  Determination  of  the  Formic  Acid. — This  may  be  effected  by 
titration  with  normal  alkali  solution  in  presence  of  phenolphthalein  (i  c.c. 
N-alkali  =0-046  gram  of   H2CO2)  and  controlled  by  the  specific  gravity 
of  the  sample.     A  marked  difference  between  the  two  results  indicates 
extraneous  acids  or  salts. 

The  formic  acid  may  be  determined  directly  as  follows  :  1-2  grams  of 
the  acid  are  neutralised  exactly  with  sodium  hydroxide,  treated  with  an 
excess  of  mercuric  chloride  solution  and  heated  on  a  steam-bath.  The 
mercurous  chloride  thus  formed  is  then  collected  on  a  tared  filter,  washed, 
dried  and  weighed  (i  gram  Hg2Cl2  =  0-0977  gram  of  H2C02). 

For  determining  the  formic  acid  in  formates,  the  latter  are  decomposed 
by  phosphoric  acid  and  distilled,  the  formic  acid  in  the  distillate  being 
determined  as  above. 

Almost  pure  formic  acid,  containing  only  traces  of  hydrochloric  acid  and 
sodium  sulphate,  may  now  be  purchased.  Some  of  the  less  pure  forms  contain 
up  to  2%  of  hydrochloric  acid.  The  mixtures  with  acetic  acid  (acetargol)  have 
been  already  mentioned. 

HYDROCHLORIC    ACID 

HC1  =  36-46  (36-5) 

The  crude  acid  of  commerce  is  more  or  less  yellow,  D  about  1-18,  con- 
taining about  35  %  HC1.  The  pure  acid  is  colourless  and  the  most  concen- 
trated has  D=ri9 — 1*20  with  a  content  of  37—39%  HC1. 

The  crude  acid  may  contain  sulphuric  acid,  chlorine,  bromine,  iodine, 
arsenic,  iron,  lime,  alkalies,  and  organic  matter.  The  pure  acid  may  contain 
the  same  impurities  but  naturally  in  smaller  proportions. 

Its  analysis  includes  the  following  : 

1.  Fixed  Residue. — 50  c.c.  are  evaporated  in  a  platinum  dish  and 
the  residue,  if  appreciable,  weighed. 

2.  Sulphuric  and  Sulphurous  Acids. — 10  c.c.,  diluted  with  50  c.c. 
of  water,  are  treated  with  barium  chloride  ;    no  turbidity  should  appear 
even  after  12  hours.     Addition  of  a  few  drops  of  chlorine  water  to  the 
liquid,  filtered  if  necessary,  will  cause  turbidity  if  sulphurous  acid  is  present. 

Sulphurous  acid  may  also  be  detected  by  treating  the  acid  with  a  piece 
of  pure  zinc  and  testing  the  gas  evolved  for  hydrogen  sulphide  by  means 
of  lead  acetate  paper. 

The  sulphuric  acid  may  be  determined  quantitatively  by  precipitation 
as  barium  sulphate  (i  gram  BaSO4  =  0-34335  gram  SO3). 

3.  Arsenic. — i  c.c.  of  the  acid  is  treated  with  5  c.c.  of  Bettendorf's 
reagent  (see  note  on  p.  18)  and  note  made  if  the  liquid  colours  within  an 
hour. 


HYDROFLUORIC  ACID  27 

For  the  quantitative  determination  of  arsenic  in  the  crude  acid,  20  c.c. 
are  diluted  with  as  much  water  and  approximately  neutralised  with  sodium 
carbonate.  A  little  ammonia  and  then  yellow  ammonium  sulphide  are 
added  and  after  acidifying  with  pure  hydrochloric  acid,  the  liquid  is  heated 
on  a  steam-bath  and  a  current  of  hydrogen  sulphide  passed  through  it  for 
2  hours.  The  precipitated  arsenic  sulphide  is  collected,  washed,  dissolved 
in  potassium  hydroxide  solution,  oxidised  with  bromine,  precipitated  with 
magnesia  mixture  and  weighed  as  magnesium  pyroarsenate.  I  gram 
of  the  pyroarsenate  =  0-48387  gram  As. 

4.  Metals. — 10  c.c.,  diluted  with  50  c.c.  of  water,  are  treated  with 
hydrogen   sulphide,   with  ammonia  and  ammonium  sulphide,   and  with 
ammonium  oxalate  ;    pure  acid  exhibits  no  change  with  these  reagents. 
Iron  is  also  easily  detected  by  means  of  potassium  feirocyanide  (deep  blue 
coloration  or  precipitate). 

5.  Chlorine. — 5  c.c.  of  dilute,  fresh  starch  paste  are  treated  with  a 
few  drops  of  10%  potassium  iodide  solution  absolutely  free  from  iodate 
and  a  few  drops  of  dilute  sulphuric  acid.     On  addition  of  i  c.c.  of  the  hydro- 
chloric acid,  diluted  with  water,  a  blue  coloration  forms  in  presence  of 
free  chlorine. 

6.  Bromine  and  Iodine  or  the  Corresponding  Acids. — 20  c.c.  of 
the  acid  are  neutralised  with  soda  and  evaporated  to  dryness,  the  residue 
being  taken  up  in  a  little  water,  a  little  fresh  chlorine  water  added  and  the 
liquid  shaken  with  carbon  disulphide  ;    in  presence  of  bromine  or  iodine 
the  carbon  disulphide  becomes  yellow  or  violet. 

7.  Determination  of  the  Hydrochloric  Acid. — With  the  pure  acid, 
it  is  sufficient  to  determine  the  acidity  with  a  standard  alkali  (i  c.c.  N-alkali 
=  0-0365  gram  HC1)  or  to  measure  the  specific  gravity  and  then  deduce 
the  acid  content  by  means  of  tables.     When  the  acid  is  not  pure,  the  esti- 
mation is  made  by  precipitating  with  silver  nitrate  either  gravimetrically 
or  volumetricaUy  by  Volhard's  method  (see  p.  10). 

*** 

The  crude  acid  may  contain  marked  amounts  of  sulphuric  acid  (up  to  about 
9%  SO  3),  but  for  technical  purposes  the  content  should  not  exceed  1-5%.  Con- 
siderable quantities  of  arsenic  (up  to  10  grams  per  100  kilos,  according  to  Buch- 
ner)  may  also  be  found  and  small  amounts  of  iron.  The  pure  acid  may  contain 
traces  of  sulphuric  acid  which  should  not,  however,  exceed  i  m.  grm.  per  100 
grams  of  the  acid  ;  no  trace  of  arsenic,  iron  or  chlorine  should  be  present. 
According  to  the  Italian  Pharmacopoeia,  10  c.c.  should  leave  no  trace  of  residue 
on  evaporation. 

HYDROFLUORIC    ACID 

HF  -20 

Aqueous  solutions  containing  60-65%  by  weight  of  HF  (D  =  I-23-I-263) 
or  5°%  or  40%  (D  =  1-189  —  I>I5I)  are  sold.  It  is  a  colourless  liquid, 
fuming  in  the  air,  of  irritating  caustic  odour.  It  is  kept  in  vessels  of  gutta- 
percha,  hardened  rubber  or,  better,  of  paraffin.  It  may  be  contaminated 
with  sulphuric,  hydrochloric,  nitric  and  hydrofluosilicic  acids,  arsenic,  heavy 
and  earthy  metals  and  organic  matter  (derived  especially  from  the  vessels). 


28  LACTIC  ACID 

1.  Sulphuric  Acid. — 3  grams,  diluted  with  10  c.c.  of  water,  are  treated 
with  2  c.c.  of  cone,  hydrochloric  acid  and  a  few  drops  of  barium  chloride 
solution  :    no  turbidity  should  be  produced  within  an  hour. 

2.  Hydrochloric  Acid. — 2  grams,  diluted  as  above,  are  treated  with 
silver  nitrate  :    no  opalescence  should  result. 

3.  Nitric  Acid. — To  4-5  c.c.  of  the  acid  are  added  a  little  copper  turn- 
ings and  about  i  c.c.  of  cone,  sulphuric  acid  ;  the  liquid  is  then  heated  and 
any  evolution  of  red  fumes  observed. 

4.  Hydrofluosilicic  Acid. — To  4-5  c.c.  of  the  acid  is  added  saturated 
potassium  chloride  solution  :   in  presence  of  hydrofluosilicic  acid,  a  white, 
gelatinous  precipitate  is  formed. 

5.  Arsenic,  Heavy  Metals,  etc. — 5  grams  of  the  acid  are  diluted  with 
20  c.c.  of  water,  the  liquid  heated  and  a  current  of  hydrogen  sulphide  passed 
through  :    a  yellow  (arsenic)  or  brown  precipitate  (heavy  metal)  may  be 
formed. 

5  grams  are  diluted  with  50  c.c.  of  water,  rendered  alkaline  with 
ammonia  and  treated  separately  with  ammonium  sulphide,  ammonium 
carbonate  and  ammonium  phosphate  for  the  detection  of  iron,  lime  and 
magnesia. 

6.  Fixed  Residue. — 10  grams  are  evaporated  in  a  platinum  dish. 

7.  Organic    Matter. — Acid     containing    this    decolorises     potassium 
permanganate  solution. 

The  pure  acid  should  leave  no  weighable  fixed  residue. 

HYDROFLUOSILICIC  ACID 

H2SiF6  =  I44-3 

This  occurs  commercially  in  7-10%  solution  (D  =  1-05-1-08)  or  in 
greater  concentrations  up  to  20  or  about  35%  (D  =  1-17-1-33).  It  may 
contain  sulphuric  acid  and  heavy  metals  as  impurities. 

1.  Sulphuric  Acid. — 5  c.c.,  diluted  with  an  equal  volume  of  water, 
and  treated  with  strontium  nitrate  solution  (free  from  barium),  should  not 
become  turbid,  even  on  standing. 

2.  Metals. — 5  c.c.  should  leave  no  appreciable  residue  on  evaporation 
in  a  platinum  dish.     5  c.c.,  diluted  with  as  much  water  and  a  few  drops 
of  hydrochloric  acid,  should  remain  unchanged  by  hydrogen  sulphide,  even 
after  being  rendered  alkaline  with  ammonia. 

3.  Quantitative   Determination. — This  is   effected  by  precipitating 
as  potassium  fluosilicate  or  by  titration  with  N/2-alkali  at  the  boiling  point 
in  presence  of  phenolphthalein,  or  in  the  cold  in  presence  of  methyl  orange 
and  25  c.c.  of  22%  calcium  chloride  solution,     i  c.c.  N/2-alkali  —  0-012 
gram  H2SiF6. 

LACTIC    ACID 

H6C3O3  =90 

A  syrupy,  odourless,  colourless,  highly  acid  liquid,  soluble  in  all  pro- 
portions in  water,  alcohol  or  ether,  but  insoluble  in  benzene  or  chloroform. 
The  pure  acid  generally  contains  75-80%  of  the  acid  (D  =  1-21-1-23),  the 


NITRIC  ACID  29 

remainder  being  water.  The  crude  acid,  also  found  on  the  market,  is  yellow- 
ish or  brown  and  contains  20-50%  of  the  acid.  The  ordinary  impurities 
are  various  mineral  acids  and  salts,  organic  acids  (acetic,  butyric,  tartaric, 
citric),  sugars,  glycerine,  mannitol. 

1.  Extraneous  Acids. — The  acid  diluted  in  the  proportion  i  :  10  and 
acidified  with  nitric  acid,  should  give  no  turbidity  with  barium  nitrate 
(sulphuric  acid  or  sulphate)  or  with  silver  nitrate  (hydrochloric  acid  or  chloride). 

i  part  of  the  acid  is  diluted  with  5  parts  of  96%  alcohol  and  filtered, 
the  filtrate  being  treated  with  a  little  hydrochloric  acid  and  a  few  c.c.  of 
10%  calcium  chloride  solution  and  boiled  :  the  presence  of  free  sulphuric 
acid  is  indicated  by  a  turbidity  appearing  either  immediately  or  after  a 
short  time. 

When  distilled  with  steam,  the  acid  should  give  a  distillate  which  is 
not  rendered  turbid  by  silver  nitrate  (free  hydrochloric  acid}. 

i  c.c.  of  the  acid,  neutralised  with  about  60  c.c.  of  lime  water,  should 
not  become  turbid  either  in  the  cold  (oxalic,  tartaric  or  phosphoric  acid)  or 
in  the  hot  (citric  acid). 

i  c.c.,  gently  heated,  should  not  evolve  an  odour  of  fatty  acids  (acetic, 
butyric  acids). 

2.  Mineral  Salts. — The  acid  diluted  in  the  proportion  i  :  10  should 
not  change  with  hydrogen  sulphide,  or  ammonia  and  ammonium  sulphide 
or  oxalate,  or  potassium  ferrocyanide  (copper,  lead,  zinc,  calcium,  iron). 

10  c.c.,  carefully  calcined,  should  leave  no  appreciable  residue. 

3.  Various  Impurities. — i  c.c.,  poured  by  drops  into  2  c.c.  of  ether, 
should  dissolve  to  a  clear  liquid  (absence  of  sugars,  mannitol,  gum,  calcium 
phosphate,  etc.). 

i  c.c.,  neutralised  with  magnesium  oxide,  evaporated  to  dryness  on 
a  steam  bath,  and  the  residue  taken  up  in  absolute  alcohol,  filtered  and 
evaporated,  should  leave  no  sweet,  syrupy  residue  (glycerine). 

i  c.c.,  mixed  carefully  (avoiding  rise  of  temperature)  with  i  c.c.  of 
cone,  sulphuric  acid,  should  not  produce  a  brown  coloration  (sugars). 

4.  Quantitative  Determination. — In  absence  of  other  acids,  the  lactic 
acid  may  be  estimated  by  means  of  a  standard  alkali  :    to  10  c.c.  (or  10 
grams)  are  added  20  c.c.  of  N-sodium  hydroxide  and  a  few  drops  of  phenol- 
phthalein  and  the  liquid  boiled  for  10  minutes  and  the  excess  of  alkali 
titrated  with   normal  hydrochloric  acid  :     i   c.c.   N-NaOH  =  0-09  gram 

^S^le^S- 

With  crude,  impure  products,  the  lactic  acid  is  estimated  by  Ulzer  and 
Seidel's  method,1  which  consists  in  oxidising  by  means  of  alkaline  potassium 
permanganate  and  then  determining  the  oxalic  acid  formed.  The  presence 
of  oxalic  acid  or  of  glycerine  must,  of  course,  be  excluded. 

NITRIC    ACID 

HNOs  =  63 

This  is  found  in  commerce  as  crude  or  commercial  acid,  usually  yellowish, 
D  =  1-33-1-40,  containing  52-65%  HN03 ;  as  pure  acid,  which  is  colourless 

1  Chem.  Zeit.,   1897,  p.  204. 


30  OXALIC  ACID 

and  of  variable  specific  gravity  but  usually  1-4  or  1-5-1 -52,  containing  65% 
or  94-99-5%  HNO3 ;  as  fuming  acid,,  which  is  reddish-yellow  or  reddish- 
brown  and  emits  dense  reddish  fumes  in  the  air,  D  =  1-48-1-52  (86-99% 
HN03)  and  is  a  mixture  of  nitric  acid  with  nitrogen  tetroxide  and  nitrous 
acid  (the  latter  in  small  quantity,  especially  in  the  very  dark  fuming  acid). 
The  usual  impurities  to  be  sought  for  in  nitric  acid  are  :  sulphuric  and 
hydrochloric  acids,  heavy,  earthy  and  alkali  metals,  iodine  and  its  com- 
pounds and  nitrous  compounds. 

1.  Sulphuric  Acid. — 10  c.c.  are  evaporated  on  a  steam-bath  to  i  c.c., 
then  diluted  with  10  c.c.  of  water  and  tested  with  barium  nitrate  :    no 
turbidity  should  appear. 

2.  Hydrochloric  Acid. — i  c.c.,  diluted  with  5  c.c.  of  water,  should 
give  no  turbidity  with  silver  nitrate. 

3.  Metals. — Diluted   in   the   ratio    i  :  2   and   rendered   alkaline   with 
ammonia,  the  acid  should  not  be  changed  by  ammonium  sulphide  or  oxalate. 

i  c.c.,  diluted  with  10  c.c.  of  water,  should  give  no  immediate  colora- 
tion with  potassium  ferrocyanide  (if on}. 

50  c.c.,  evaporated  on  a  steam-bath,  should  give  no  appreciable 
residue. 

4.  Iodine  (lodic  Acid). — i  c.c.,  diluted  with  2  c.c.  of  water  and  shaken 
with  a  few  drops  of  chloroform,  should  give  no  coloration  to  the  latter, 
even  after  addition  of  a  fragment  of  zinc. 

5.  Nitrous  Compounds. — To  5  c.c.  of  the  acid,  diluted  with  5  volumes 
of  water,  are  added  a  few  drops  of  normal  potassium  permanganate  solution, 
which  is  decolorised  if  nitrous  compounds  are  present. 

For  the  quantitative  determination  of  nitrous  compounds  in  the  fuming 
acid,  Lunge  and  Marchlewski's  method  may  be  followed  :  From  a  well- 
calibrated,  narrow  burette,  divided  into  -^  c.c.  so  that  o-oi  c.c.  can  be 
readily  measured,  the  acid  is  allowed  to  fall  drop  by  drop  into  a  measured 
volume  of  seminormal  permanganate  solution  (15-803  grams  KMnO4  per 
litre)  kept  at  40°,  until  decolorisation  occurs.  Before  the  titration  the 
acid  is  left  for  some  time  in  the  burette  to  assume  the  air-temperature, 
which  is  measured  with  an  accurate  thermometer.  The  number  of  c.c.  of  acid 
taken,  multiplied  by  its  specific  gravity  determined  at  the  temperature  of 
titration,  gives  the  weight  of  acid  used  in  the  titration.  The  nitrous  com- 
pounds, calculated  as  N2O4,  are  expressed  per  100  parts  of  the  acid.  The 
titre  of  the  permanganate  is  determined  by  means  of  iron  in  the  ordinary 
way.  i  c.c.  N/2-permanganate  =  0-023  gram  N2O4. 

In  acid  for  technical  purposes  the  presence  of  nitrous  products  is  allowed 
— in  that  used  in  dynamite  factories  to  the  extent  of  2%  (Guttmann). 

OXALIC    ACID 

H2C2O4  +  2H2O  =  126-05  (126) 

Colourless  crystals,  soluble  in  about  10  parts  of  cold  water  or  2-5  of 
boiling  water,  and  in  alcohol.  Its  most  frequent  impurities  are  sulphates, 
chlorides,  ammonia,  alkalies  and  calcium,  and  sometimes  small  quantities 
of  copper,  lead  and  iron. 


PHOSPHORIC  ACID  31 

1.  Sulphates,  Chlorides. — Separate  portions  of  the  i  :  10  solution, 
acidified  with  nitric  acid,  should  not  become  turbid  with  barium  chloride 
or  silver  nitrate. 

2.  Ammonia. — 2  grams,  heated  with  excess  of  caustic  soda,  should 
yield  no  ammoniacal  odour. 

2  grams  dissolved  in  30  c.c.  of  water,  neutralised  with  sodium 
hydroxide  and  made  up  to  50  c.c.,  should  give  no  coloration  with  10-15 
drops  of  Nessler  solution. 

3.  Metals. — The  i  :  10  solution  should  not  become  turbid  (calcium) 
when  rendered  alkaline  with  ammonia  or  after  further  addition  of  ammonium 
sulphide  (copper,  lead,  iron). 

10  grams,  heated  in  a  platinum  crucible,  should  volatilise  without 
turning  brown  or  leaving  appreciable  residue.  Any  residue  left  should  be 
tested  for  alkali  metals. 


PHOSPHORIC    ACID 

H3PO4  =  98-024  (98) 

Ordinary  phosphoric  acid  or  orthophosphoric  acid  is  a  colourless,  odour- 
less liquid  with  density  varying  according  to  the  concentration  (1-73  = 
90%  ;  172  =  86%  ;  1-44  =  60%  ;  1-35  =  50%  ;  1-26  =  40%  ;  1-15  = 
25%).  The  impurities  to  be  tested  for  in  the  commercial  acid  are  :  sul- 
phuric, nitric,  hydrochloric,  metaphosphoric  and  phosphorous  acids, 
ammonia,  arsenic,  heavy  and  earthy  metals  and  organic  matter. 

1 .  Sulphuric  Acid . — The  dilute  acid  (i :  2)   is  treated  with  barium 
chloride  in  the  hot :    no  turbidity  should  appear,  even  after  standing. 

2.  Nitric  Acid. — The  dilute  acid  (i  .  i)  is  treated  with  a  few  drops 
of  a  sulphuric  acid  solution  of  diphenylamine  :  no  blue  coloration  should 
appear,     i    c.c.   of  the  acid  +  3  c.c.   of  water  should  not  decolorise  a 
drop  of  a  sulphuric  acid  solution  of  indigo. 

3.  Hydrochloric  Acid. — The  acid,  diluted  with  5  vols.  of  water  and 
treated  with  silver  nitrate  in  the  cold,  should  give  no  turbidity. 

4.  Phosphorous  Acid. — To  the  acid,  somewhat  diluted,  silver  nitrate 
is  added  and  the  liquid  heated  to  boiling  ;  in  presence  of  phosphorous  acid, 
blackening  is  observed.     Also,  the  acid  is  heated  with  mercuric  chloride, 
which  gives  a  white  precipitate  of  calomel  in  presence  of  phosphorous  acid. 

5.  Metaphosphoric  Acid. — The  diluted  acid  is  added  to  a  dilute  solu- 
tion of  albumin  :   a  turbidity  is  formed  if  metaphosphoric  acid  is  present. 

6.  Ammonia. — The  acid  is  heated  with  excess  of  caustic  soda  and  the 
odour  of  the  evolved  vapour  noted. 

7.  Arsenic. — When  tested  for  an  hour  in  the  Marsh  apparatus  (see 
Flesh  Foods,  Vol.  II),  the  acid  should  give  no  arsenic  ring ;    I  c.c.  of  the 
acid  with  5  c.c.  of  Bettendorf's  reagent  (see  note  on  p.  18)  should  give  no 
coloration  within  an  hour. 

8.  Heavy  and  Earthy  Metals. — The  acid  is  subjected  to  a  cuirent 
of  hydrogen  sulphide.     Another  portion,  greatlytliluted,  is  rendered  alkaline 
with   ammonia   and   then   tested   with   ammonium  sulphide,   ammonium 


32  PICRIC  ACID 

oxalate,  etc.     A  third  portion  is  mixed  with  4  vols.  of  alcohol.     In  no  case 
should  a  precipitate  form. 

9.  Organic  Matter. — When  strongly  heated  in  a  dish,  the  acid  blackens 
if  organic  substances  are  present.  5  c.c.  of  the  acid  are  boiled  for  5 
minutes  with  5  c.c.  of  dilute  silphuric  acid  and  5  drops  of  0*1%  perman- 
ganate :  in  presence  of  organic  matter,  the  liquid  becomes  decolorised 
(the  decoloration  may,  however,  depend  on  lower  acids  of  phosphorus, 
arsenious  acid,  etc.). 

*** 

Metaphosphoric  or  glacial  phosphoric  acid  (HPO3  =  80)  is  sold  in  glassy 
masses  or  rods.  It  may  contain  the  same  impurities  as  ordinary  phosphoric 
acid  but  is  contaminated  more  particularly  with  sodium  metaphosphate, 
often  in  considerable  quantities.  This  impurity  is  detected  by  dissolving 
the  acid  in  concentrated  hydrochloric  acid  (D  =  1-19)  :  the  presence  of 
the  sodium  salt  leads  to  the  formation  of  sodium  chloride,  which  remains 
undissolved. 

PICRIC    ACID 

H3C6N307  =  229 

Lemon-yellow,  crystalline  scales  or  powder,  m.pt.  122-123°,  soluble 
in  25  parts  of  cold  water,  readily  soluble  in  boiling  water,  alcohol,  ether 
or  benzene.  The  commercial  acid  may  contain,  as  impurities,  resinous 
matters,  oxalic  acid,  sulphates,  chlorides  and  mono-  and  di-nitrophenols, 
and  may  be  adulterated  with  considerable  quantities  of  alum,  magnesium 
sulphate,  sodium  sulphate  and  sodium  chloride. 

1.  Resinous  and  Various  Insoluble  Substances. — 4  grams  of  the 
acid  are  boiled  with  100  c.c.  of  water  until  completely  dissolved,  any  insoluble 
residue  being  collected  on  a  tared  filter  and  weighed. 

2.  Various  Mineral  Salts. — 4  grams  of  the  acid  are  treated  with  100 
c.c.  of  ether,  any  insoluble  residue  being  collected,  weighed  and  analysed, 
tests  being  made  especially  for  magnesium  sulphate,  alum,  sodium  sulphate 
and  sodium  chloride. 

3.  Oxalic  Acid. — 4  grams  dissolved  in  hot  water  (about  250  c.c.)  are 
neutralised  with  ammonia  and  tested  with  calcium  chloride. 

4.  Sulphuric  Acid. — 4  grams,  dissolved  in  250  c.c.  of  water,  are  tested 
with  barium  chloride. 

5.  Hydrochloric  Acid. — 4  grams,  dissolved  in  250  c.c.  of  water  and 
acidified  with  nitric  acid,  are  tested  with  silver  ritrate  solution. 

6.  Mono-    and    di-nitrophenols. — Into    two    bottles    with    ground 
stoppers  are  poured  equal  volumes  of  i%  bromine  water,  into  one  of  them 
a  i%  solution  of  the  picric  acid  and  then  into  each  excess  of  potassium 
iodide.     The  iodine  liberated  in  each  case  is  titrated  with  N/io-thiosulphate 
and  from  the  bromine  combined  the  content  of  these  two  impurities  cal- 
culated. 

The  pure  acid  should  not  leave  more  than  0-1%  of  residue  insoluble  in  water 
or  0-2%  insoluble  in  ether.  Only  traces  of  oxalic  acid  or  hydrochloric  acid 
should  be  found,  and  the  sulphuric  acid  should  not  exceed  0-05%. 


SULPHURIC  ACID  33 

SULPHURIC    ACID 

H2SO4  =  98-08  (98) 

This  is  sold  in  various  degrees  of  concentration  and  purity  :  Chamber 
acid  of  50-53°  Baume,  D  =  1-53-1-58,  with  62-67%  H2SO4 ;  acid  of  60° 
Baume,  D  =  1-71,  with  78%  H2S04  ;  ordinary  English  acid  of  66°  Baume, 
D  =  1-84,  with  93-96%  ;  extra  concentrated,  with  96-98%  and  the  mono- 
hydrate,  with  99-5%.  As  regards  the  purity,  there  is  more  or  less  impure 
commercial  acid,  containing  more  especially  lead,  iron,  arsenic,  sulphurous 
acid,  nitrous  products  and  organic  matter  as  impurities,  and  the  pure  or 
puriss.  acids  which  should  not  contain  the  above  or  other  foreign  substances. 

1.  Fixed  Residue. — 10  c.c.  are  evaporated  and  calcined  in  a  platinum 
dish  and  any  residue  analysed  in  the  ordinary  way,  especially  for  heavy 
and  alkali  metals. 

2.  Lead,  Iron  and  other  Heavy  Metals. — i  vol.  of  the  acid  is  poured 
carefully  into  5  vols.  of  90%  alcohol :  no  heavy,  white  deposit  (lead  sulphate) 
should  be  formed,  even  after  some  hours. 

5  c.c.  are  heated  with  a  few  drops  of  nitric  acid,  allowed  to  cool, 
diluted  with  water  and  tested  with  potassium  thiocyanate  :  no  red  coloration 
(iron)  should  be  observed. 

i  c.c.,  diluted  with  20  c.c.  of  water,  should  give  no  brown  coloration 
with  hydrogen  sulphide  (copper,  lead),  and  after  being  made  alkaline  with 
ammonia  should  not  become  brown  (iron)  or  turbid  (zinc}. 

3.  Arsenic. — When  used  in  the  Marsh  apparatus   (see  Flesh  Foods, 
Vol.  II)  for  an  hour,  the  acid  should  yield  no  arsenical  mirror. 

i  c.c.,  diluted  with  2  c.c.  of  water  and  treated  with  5  c.c.  of  Betten- 
dorf's  reagent  (see  p.  18),  should  not  become  coloured  within  an  hour. 

The  quantitative  determination  is  carried  out  as  follows  :  20  grams  of  the 
acid  are  diluted  with  an  equal  volume  of  water  and  a  current  of  sulphur  di- 
oxide passed  through  the  liquid  until  the  latter  smells  strongly  of  it.  The 
excess  of  sulphur  dioxide  is  then  expelled  by  means  of  carbon  dioxide,  a  little 
bicarbonate  added  and  the  arsenious  acid  titrated  with  N/io-iodine  and 
starch  paste,  i  c.c.  N/io-iodine  =  0-00495  gram  As2O3.  If  iron  is 
present  in  more  than  negligible  amount,  it  must  be  eliminated  before  apply- 
ing this  method. 

4.  Selenium. — 10  c.c.  of  the  acid,  diluted  with  30  c.c.  of  water,  are 
treated  with  20  c.c.  of  saturated  sulphur  dioxide  solution  :   in  presence  of 
selenium  a  reddish-yellow  coloration  appears,  a  slight  red  precipitate  being 
gradually  deposited  later  (if  the  selenium  is  not  too  small  in  amount). 

5.  Ammonia. — 2  c.c.  of  acid  are  diluted  with  about  30  c.c.  of  water, 
then  rendered  alkaline  with  sodium  hydroxide  solution  and  tested  with 
Nessler  solution  (see  Potable  Waters). 

6.  Sulphurous  Acid. — Starch  paste  is  turned  blue  by  a  little  dilute 
iodine  solution  and  the  acid  to  be  tested  diluted  and  then  added  to  the 
starch,  which  is  decolorised  in  presence  of  sulphurous  acid.     Or  the  acid 
may  be  diluted,  a  granule  of  zinc  added  and  the  liquid  warmed  :  evolution 
oi  hydrogen  sulphide  is  then  tested  for  by  means  of  lead  acetate  paper. 

7.  Nitrous    Compounds,    Nitric    Acid. — Ferrous   sulphate  solution 

A.C.  3 


34  FUMING  SULPHURIC  ACID 

is  poured  on  to  the  undiluted  acid  and  the  surface  of  contact  of  the  two 
liquids  examined  for  a  brown  ring.  Very  small  quantities  of  nitrous  com- 
pounds or  of  nitric  acid  may  be  detected  respectively  by  Griess's  reagent 
(see  Waters,  p.  6)  or  diphenylamine  used  as  follows  :  on  to  a  few  crystals  of 
pure  diphenylamine  in  a  dry  test-tube  are  poured  a  few  c.c.  of  the  acid  to 
be  tested  and  on  this  as  much  distilled  water  so  that  two  layers  are 
formed  :  the  zone  of  contact  of  the  two  layers  should  show  no  blue  colora- 
tion, even  after  standing. 

8.  Hydrochloric  Acid.— The  diluted  acid  is  treated  with  silver  nitrate. 

9.  Hydrofluoric  Acid. — The  acid  is  warmed  in  a  platinum  dish  covered 
with  a  glass  coated  with  wax  which  has  been  scratched  so  as  to  ur  cover 
the  glass  in  places  :    if  hydrofluoric  acid  is  present,  the  naked  glass  is 
attacked. 

10.  Reducing  Substances   (Organic  Matter,  Sulphurous  and  Nitrous 
Acids). — 15  c.c.  of  the  acid  are  diluted  with  45  c.c.  of  water  and  a  drop  of 
decinormal  permanganate  solution  added  :    the  pink  colour  should  persist 
for  5  minutes. 

11.  Quantitative  Determination. — In   absence  of  other  acids,   the 
sulphuric  acid  may  be  titrated  with  N-alkali ;   i  c.c.  =  0-04904  gram  H2S04. 
When  other  acids  are  present,  precipitation  as  barium  sulphate  must  be 
employed. 

Crude  commercial  sulphuric  acid  always  contains  arsenic  and  usually  from 
0-8  to  4-4  grams  per  100  kilos,  although  as  much  as  0-5%  has  been  found. 

FUMING    SULPHURIC    ACID 
(OLEUM) 

This  is  a  mixture  of  the  monohydrate  (H2S04)  with  sulphuric  anhydride 
and  is  an  oily  liquid,  rarely  colourless  but  more  often  brownish  ;  it  fumes 
in  the  air  and  is  more  or  less  turbid  and  often  partly  or  completely  crys- 
tallised. Analysis  of  this  acid  includes  the  determinations  described  for 
ordinary  sulphuric  acid ;  further,  in  order  to  know  exactly  its  value,  its 
content  of  sulphuric  anhydride,  monohydrate  acid  and  sulphurous  acid, 
where  this  is  present,  must  be  known.  Lunge's  method,  which  is  as  follows, 
may  be  used. 

From  3  to  4  grams  of  the  fuming  acid,  weighed  by  means  of  Lunge  and 
Key's  special  bulb  pipette  or  any  similar  instrument  and  with  all  the  necessary 
precautions,  is  dissolved  in  about  half  a  litre  of  very  cold  water  and,  when 
the  liquid  has  assumed  the  air-temperature,  the  volume  made  up  to  500 
c.c.  In  100  c.c.  of  this  solution  the  total  acidity  is  determined  by  means 
of  N/2— caustic  soda  solution  and  methyl  orange.  In  another  100  c.c., 
any  sulphurous  acid  is  determined  by  N/io— iodine  and  starch  paste.  The 
sulphuric  anhydride  and  monohydrated  sulphuric  acid  are  then  calculated 
as  follows  : 

(a)  In  absence  of  S02 :  Ihe  total  acidity  is  calculated  as  percentage  of 
SO3 ;  i  c.c.  N/2-NaOH  =  0-02003  gram  SO3.  The  sulphuric  anhydride 
thus  calculated  is  then  subtracted  from  100,  the  difference  representing 
the  water  in  100  parts  of  the  substance.  From  the  quantity  of  water  thus 


TARTARIC   ACID  35 

found  the  monohydrate  is  calculated,  18  parts  of  water  corresponding  with 
98  of  H2SO4.  Finally,  subtraction  of  the  percentage  of  H2SO4  from  100 
gives  the  free  SO3. 

(b)  In  presence  of  SOZ :  in  this  case  the  total  acidity  must  be  diminished 
by  that  due  to  the  sulphurous  acid,  that  is,  before  calculating  the  SO3  from 
the  acidity,  the  number  of  c.c.  of  N/io-iodine  used  in  determining  the 
sulphurous  acid  is  divided  by  10  and  the  result  subtracted  from  the  number 
of  c.c.  of  N/2-soda  used  in  the  measurement  of  the  acidity  1  ;  from  the 
number  thus  obtained  the  SO3  is  calculated  as  in  (a).  The  sum  of  the  SO3 
thus  found  and  of  the  SO2  found  directly  (i  c.c.  N/io-iodine  =  0-0032  gram 
of  SO  2)  is  subtracted  from  100,  the  result  being  the  water,  from  which  the 
H2SO4  is  calculated  as  in  the  previous  case.  Lastly,  the  SO3  is  calculated 
by  subtracting  from  100  the  sum  of  the  H2SO4  and  the  SO2. 

Example  (of  case  b)  :  3^422  grams  of  fuming  acid,  dissolved  in  water,  were 
made  up  to  500  c.c.  For  100  c.c.  of  this  solution  (=  0-6844  gram  of  substance) 
30-10  c.c.  of  N/2-caustic  soda  were  required,  or  5-25  c.c.  of  N/io-iodine.  Then 

30-10  —  0-525  =  29-575, 
so  that  the  SO3  will  be 

29-575  X  0-02003  =  0-5924, 
or,  allowing  for  the  amount  of  the  fuming  acid  in  100  c.c., 

SO  3  =  86-56%. 
On  the  other  hand  the  sulphurous  acid  will  be 

5-25  X  0-0032  =  0-0168 

i.e.,  SO  2=  2-46%. 

Hence  the  water  will  be 

100  —  (86-56  +  2-46)  =  10-98. 
To  10-98  of  water  there  correspond  59-78  of  H2SO4,  since 

18  :  98  :  :  10-98  :  59-78. 
The  free  SO3  will  therefore  be 

100  —  (59-78  +  2-46)  =  37-76. 
The  acid  thus  contains 

H2S04  59-78% 

S03  37-76% 

SO  2  2-46% 

TARTARIC    ACID 

C4H606  =  150 

Large,  colourless,  transparent,  odourless,  non-hygroscopic  crystals  of 
acid  taste,  readily  soluble  in  water  or  alcohol.  It  may  be  contaminated 
especially  by  small  quantities  of  sulphuric  acid  or  sulphates,  salts  of  calcium, 
potassium,  iron,  copper,  and  particularly  lead,  and  sometimes  arsenic.  It 
may  be  adulterated  with  cream  of  tartar,  potassium  and  sodium  sulphates, 
alum  and  oxalic  acid. 

The  tests  to  be  made  are  as  follows  : 

1.  Solubility. — It  should  dissolve  completely  in  water  (absence  of 
calcium  tartrate  or  sulphate). 

1  The  reason  of  this  is  that,  when  the  acidity  is  determined  in  presence  of  sulphurous 
acid  with  methyl  orange  as  indicator,  neutrality  of  the  liquid  is  reached  when  the  acid 
sulphite,  NaHSO3,  and  not  the  normal  sulphite,  Na2SO3,  is  formed.  Consequently,  i  c.c. 
of  N/io-iodine  solution  is  equivalent  not  to  o-i  c.c.,  but  to  only  0-05  c.c.  of  N-soda  and 
therefore  to  o-i  c.c.  N/2-soda. 


36  TARTARIC  ACID 

2.  Fixed   Residue. — 2  grams  are  cautiously  calcined  in  a  platinum 
dish  and  any  residue  examined  in  the  usual  way. 

3.  Sulphuric  Acid. — The  i  :  10  solution  is  tested  with  barium  chloride. 

4.  Oxalic   Acid. — The   i  :  10  solution,  neutralised  with  ammonia,  is 
treated  with  calcium  sulphate. 

5.  Lime. — -The  i  :  10  solution  is  rendered  alkaline  with  ammonia  and 
tested  with  ammonium  oxalate. 

6.  Heavy  Metals. — The  i  :  10  solution  is  treated  with  hydrogen  sulphide 
or  neutralised  with  ammonia  and  then  treated  with  ammonium  sulphide. 

7.  Arsenic. — The  concentrated  solution  should  not  be  coloured  by 
Bettendorf's  reagent. 

8.  Quantitative   Determination. — In  absence    of  other    free  acids, 
the  aqueous  solution  of  the  acid  is  titrated  with  N-alkali  in  presence  of 
phenolphthalein  :    i  c.c.  N-alkali  =  0-07502  gram  of  tartaric  acid. 

The  pure  acid  should  leave  no  weighable  residue  :  the  Italian  Pharmacopoeia 
allows  5  parts  per  1000.  The  commercial  acid  often  contains  lead  partly  com- 
bined and  partly  free  ;  as  much  as  0-6  gram  per  kilo  has  been  found. 

Tartars  and  other  Tartaric  Substances 

These  are  mainly  wine  lees,  cask  incrustation,  crude  tartars  and  crude 
calcium  tartrate. 

Wine  lees  consist  of  a  slimy,  reddish  mass  containing  essentially  yeasts, 
cream  of  tartar,  calcium  tartrate,  colouring  matter  and  water.  Cask 
incrustations  and  crude  tartars  are  composed  of  dirty  white  or  reddish  crys- 
talline crusts  or  masses.  Crude  calcium  tartrate  is  a  greyish  or  reddish 
powder  almost  insoluble  in  water  but  soluble  in  dilute  acids. 

For  the  analysis  of  these  substances  a  homogeneous  sample  must  be 
prepared  ;  the  substance  is  well  mixed  and  powdered  so  that  it  passes 
through  at  least  a  £  millimetre  sieve. 

In  ah1  the  products  it  is  necessary  to  determine  the  tartaric  acid,  whether 
combined  with  potash  or  lime.  According  to  the  methods  adopted  at  the 
Seventh  International  Congress  of  Applied  Chemistry,  London,  1909,  the 
tartaric  acid  is  determined  as  follows  : 

1.  Determination  of  the  Tartaric  Acid  existing  as  Potassium 
Bitartrate. — 2-350  grams  of  the  substance  are  boiled  for  5  minutes  with 
about  400  c.c.  of  water  in  a  500  c.c.  flask,  a  further  quantity  of  water  being 
added  and  the  whole  allowed  to  cool,  made  up  to  volume,  mixed  and  filtered 
through  a  pleated  filter.     Of  the  filtrate  250  c.c.  (=  1-175  gram  of  substance) 
are  heated  to  boiling  and  titrated  with  N/4-caustic  alkali  standardised  by 
means  of  bitartrate  (puriss.),  using  sensitive  litmus  paper  (phenolphthalein 
may  also  conveniently  be  used). 

2.  Determination    of   the    Total    Tartaric    Acid    (Goldenberg   and 
Geromont's  method,  modified). — 6  grams  (12,  if  poor  in  tartaric  acid)  of 
material  are  weighed  and,  together  with  18  c.c.  of  HC1  (D  i-io),  introduced 
into  a  150-200  c.c.  beaker.     The  whole  is  thoroughly  mixed  and  stirred  at 
the  ordinary  temperature,  the  lumps  being  broken  with  a  glass  rod  and  the 
particles  washed  from  the  sides  of  the  beaker  with  small  quantities  of  water 
from  a  wash-bottle.     After  digestion  for  10-15  minutes,  the  whole  is  washed 


TARTARIC  ACID  37 

out  into  a  200  c.c.  flask,  made  up  to  volume,  mixed  and  filtered  through  a 
dry  filter. 

By  means  of  a  pipette  corresponding  exactly  with  the  measuring-flask, 
100  c.c.  of  the  filtrate  (=  3  grams  of  substance)  are  introduced  into  a  300 
c.c.  beaker  already  containing  10  c.c.  of  potassium  carbonate  solution  of 
density  1-490  (66  grams  of  anhydrous  carbonate  in  100  c.c.  of  solution). 
After  mixing,  the  liquid  is  slowly  heated  and  finally  boiled  for  20-25  minutes 
until  effervescence  ceases  and  the  whole  of  the  calcium  carbonate  thrown 
down  in  powder.1  After  cooling  to  the  air-temperature,  the  liquid  and 
precipitate  are  poured  into  a  200  c.c.  graduated  flask,  the  beaker  being 
washed  repeatedly  with  distilled  water.  After  making  up  to  volume  and 
mixing,  the  liquid  is  filtered  through  a  dry,  pleated  filter,  and  100  c.c.  of 
the  filtrate  (=  1-5  gram  of  substance)  evaporated  on  a  steam-bath  in  a 
400-500  c.c.  porcelain  dish  until  the  crystalline  skin  forming  at  the  edges 
no  longer  dissolves  on  gentle  shaking.  The  evaporation  is  continued  for 
some  minutes  with  movement  of  the  dish  until  a  dry  residue  is  obtained. 
This  is  redissolved  in  5  c.c.  of  boiling  water  and  4  c.c.  of  glacial  acetic  acid 
then  added  in  drops  at  the  edge  of  the  hot  liquid,  the  whole  being  stirred 
vigorously  for  5  minutes  with  a  glass  rod.  After  a  further  interval  of  10 
minutes,  100  c.c.  of  95%  alcohol  are  added  and  the  mixture  stirred  for  5 
minutes  to  render  the  precipitate  granular  and  crystalline. 

After  the  lapse  of  10  minutes,  the  alcohol  is  decanted  on  to  a  cellulose 
filter  and  drawn  through  with  a  pump.  The  precipitate  is  washed  three  or 
four  times  with  alcohol  by  decantation,  then  introduced  on  to  the  filter 
and  the  washing  continued  until  the  alcohol  passing  through  no  longer 
exhibits  an  acid  reaction. 

The  filter  and  precipitate  are  placed  again  in  the  dish  with  200-300  c.c. 
of  water,  boiled  for  a  minute,  and  titrated  in  the  hot  with  N/4-potassium 
hydroxide  (standardised  with  puriss.  bitartrate),  neutral,  sensitive  litmus 
paper  being  used  as  indicator.  The  number  of  c.c.  of  alkali  used,  multiplied 
by  10  and  divided  by  4,  gives  directly  the  percentage  of  tartaric  acid. 

The  result  obtained  must  be  corrected  for  the  volume  occupied  in  the 
solutions  by  the  insoluble  substances.  Where  12  grams  of  material  are 
taken,  the  correction  is  calculated  by  means  of  the  formula, 

y  =  i  —  o-oi  x, 

where  x  is  the  percentage  of  tartaric  acid  found  and  y  the  amount  to  be 
deducted  from  it  ;  if  6  grams  are  taken,  the  correction  is  one-half  that  given 
by  the  above  formula. 

* 

*   * 

Wine  lees  usually  contain  from  15  to  30%  of  potassium  bitartrate,  but  some- 
times as  little  as  10%  or  as  as  much  as  40%  ;  the  Italian  products  generally 
contain  about  24%  of  tartaric  acid  as  potassium  bitartrate  and  about  6%  as 
calcium  tartrate.  Cask  incrustations  contain  up  to  70-80%  of  cream  of  tartar, 
and  crude  tartar  contains  more  or  less  according  to  the  method  of  preparation  ; 

1  According  to  Perciabosco  (Staz.  agr.  Hal.,  1914,  XLVII,  p.  803),  with  material 
rich  in  tartrates  it  is  advisable  to  add  the  potassium  carbonate  to  the  boiling  hydrochloric 
acid  solution.  In  this  case  the  boiling  is  protracted  after  the  addition  of  the  carbonate 
for  only  10  minutes. 


38  METHYL  ALCOHOL 

in  both  products,  especially  those  from  plastered  wines,  variable  proportions  of 
calcium  tartrate  may  be  found.  Crude  calcium  tartrate  contains,  besides  calcium 
tartrate,  small  proportions  of  potassium  bitartrate,  gypsum,  lime,  calcium 
carbonate  and  organic  matter. 

YL    (Isoamyl)    ALCOHOL 

C5H120  =  88 

Crude  amyl  alcohol  of  commerce  constitutes  fusel  oil,  which  contains 
variable  quantities  of  amyl  alcohol  (sometimes  only  30%)  mixed  with  other 
higher  alcohols,  ethyl  alcohol,  furfural  and  other  impurities.  This  fusel 
oil  is  a  more  or  less  yellow  liquid  of  repulsive  odour. 

Pure  amyl  alcohol  of  commerce  is  a  colourless  or  yellowish  liquid  of 
peculiar,  rather  irritating  odour,  D  0-814-0-816,  b.p>t.  129-132°,  very  slightly 
soluble  in  water,  readily  in  alcohol,  ether  or  benzene.  It  almost  always 
contains  small  proportions  of  furfural  and  other  impurities.  The  tests  to 
be  made  are  as  follows  : 

1.  Density,  Boiling  Point. — By  the  ordinary  methods. 

2.  Residue. — 50  c.c.,  evaporated  on  a    steam-bath,  should  leave  no 
appreciable  residue. 

3.  Furfural,    Aldehydes. — 5    c.c.,    when   mixed   carefully   and   with 
cooling  with  an  equal  volume  of  pure  cone,  sulphuric  acid,  should  become 
neither  brown  nor  turbid  (a  slight  reddish  or  yellowish  coloration  is  per- 
missible).    The  same  result  should  be  obtained  with  concentrated  caustic 
potash  solution. 

4.  Alcohol. — This  is  detected  and  determined  as  in  amyl  acetate  (6). 

ETHYL    ALCOHOL 

See  chapter  on  Spirits  and  Liqueurs  in  Vol.  II 

METHYL    ALCOHOL 

CH40  =  32 

This  is  marketed  in  different  qualities  :  methyl  alcohol  puriss.  is  a  colour- 
less liquid,  D  0-796,  b.pt.  66°.  Commercial  methyl  alcohol  (rectified,  white 
methyl  alcohol)  is  a  colourless  or  yellowish  liquid,  b.pt.  usually  64-67°. 
Crude  methyl  alcohol  is  a  yellowish  or  brownish  liquid  with  a  more  or  less 
empyreumatic  odour  and  burning  taste,  distilling  mainly  between  60° 
and  75°. 

Distinctive  Tests. — (a)  CHARACTERS. — Crude  methyl  alcohol  is  dis- 
tinguished from  the  rectified  alcohol  (commercial  methyl  alcohol) — which 
is  colourless  or  almost  so — by  its  yellowish  or  brownish  tint,  its  empyreu- 
matic odour,  burning  taste  and  its  large  content  (15-25%)  of  acetone  (for 
the  quantitative  determination  of  acetone,  see  later). 

(b)  REACTION  WITH  SULPHURIC  ACID.  To  5  c.c.  are  added,  gradually 
and  with  cooling,  5  c.c.  of  cone,  sulphuric  acid  :  pure  methyl  alcohol  assumes 
only  a  slightly  yellow  coloration,  whilst  the  commercial  alcohol,  whether 
crude  or  rectified,  gives  immediately  a  brown  coloration. 


METHYL  ALCOHOL  39 

(c)  PERMANGANATE  TEST.  5  c.c.  of  the  alcohol  are  treated  with  i  c.c. 
of  0-1%  permanganate  solution.  With  pure  methyl  alcohol  the  pink  colora- 
tion persists,  whereas  with  the  commercial  product,  either  crude  or  rectified, 
the  permanganate  is  instantly  decolorised. 

A.     Pure  Methyl  Alcohol 

The  tests  to  be  made  are  as  follows  : 

1.  Sulphuric  Acid  Test  (vide  supra). 

2.  Permanganate  Test  (vide  supra). 

3.  Non-volatile   Substances. — 50  c.c.   evaporated  on  a    steam-bath 
should  leave  no  appreciable  residue. 

4.  Acidity  or  Alkalinity. — 15-20  c.c.  of  the  alcohol  are  mixed  with 
an  equal  volume  of  water  coloured  with  neutral  litmus,  the  colour  of  which 
should  not  be  altered  in  the  mixture. 

5.  Solubility  in  Water. — 15-20  c.c.  of  the  alcohol,  mixed  with  water 
in  any  proportion,  should  give  a  clear  solution. 

6.  Solubility  in  Caustic  Soda  Solution. — 15-20  c.c.  of  the  alcohol, 
mixed  with  concentrated  sodium  hydroxide  solution,  should  yield  a  colour- 
less solution  (absence  of  aldehydes). 

7.  Distillation. — 50  c.c.  of  the  alcohol,  when  distilled,  should  pass 
over  within  0-5°  (a  100  c.c.  copper  flask  with  side-tube  is  best). 

8.  Acetone. — i  c.c.  of  the  alcohol  is  treated  with  10  c.c.  of  10%  sodium 
hydroxide  solution  and  5  drops  of    approximately  N/io-solution  of  iodine 
in  potassium  iodide.     Even  after  some  time  no  turbidity,  due  to  iodoform, 
should  be  formed  (for  quantitative  determination,  see  later). 

9.  Determination  of  the  Methyl  Alcohol. — The  content  of  methyl 
alcohol  is  deduced  from  the  specific  gravity  by  means  of  Klason  and  Norton's 
tables  (see  page  40). 

B.     Commercial  Methyl  Alcohol,  Crude  or  Rectified 

The  tests  commonly  made  are  : 

1.  Acidity  or  Alkalinity. — The  alcohol  is  tested  with  very  sensitive 
litmus  paper  or,  if  the  product  is  colourless,  with  neutral  litmus  tincture 
or  methyl  orange. 

2.  Alcoholometric  Degree. — In  practice  use  is  made  of  Gay-Lussac's 
alcoholometer  at  15°  or  that  of  Tralles  at  15-56°.   Although  these  alcoholo- 
meters are  graduated  for  ethyl  alcohol,  they  are  used  for  methyl  alcohol, 
aqueous  mixtures  of  the  latter  having  densities  approximating  to  those 
of  water-ethyl  alcohol  mixtures. 

3.  Distillation. — This  is  carried  out  on  100  c.c.,  using  the  flask  described 
for  the  distillation  of  pyridine  bases  (see  chapter  on  Tar  and  its  Products), 
the  fractions  distilling  over  for  each  5°  being  collected  separately  in  graduated 
cylinders. 

4.  Solubility  in  Water. — 10  c.c.  are  mixed  in  a  100  c.c.  cylinder  with 
10  c.c.  of  water  and  any  turbidity  noted  ;   30  c.c.  of  water  are  then  added, 
and  later  further  quantities  to  100  c.c.,  any  formation  of  opalescence  being 
observed. 


METHYL  ALCOHOL 


TABLE  III 
Specific   Gravities  of  Methyl  Alcohol 


Specific 
Gravity 
at  15°  C. 

%  of  Methyl 
Alcohol. 

Specific 
Gravity 
at  15°  C. 

%  of  Methyl 
Alcohol. 

Specific 
Gravity 
at  15°  C. 

%  of  Methyl 
Alcohol. 

By 

Weight. 

By 

Volume. 

By 

Weight. 

By 

Volume. 

By 

Weight. 

By 

Volume. 

07964 

100  -oo 

loo  -oo 

0-8650 

74*49 

80-89 

0-9350 

41-79 

49-01 

0-7975 

99-64 

99-77 

0-8675 

73-49 

80-02 

0-9375 

40-40 

47-53 

o  -8000 

98-75 

99-18 

0-8700 

72-48 

79-13 

0-9400 

39-00 

45-94 

0-8025 

97-85 

98-59 

0-8725 

71-44 

78-23 

0-9425 

37-54 

44-29 

0-8050 

96-96 

98-01 

0-8750 

70-38 

77-31 

0-9450 

36-03 

42-66 

0-8075 

96-07 

97-41 

0-8775 

69-31 

76-39 

0-9475 

34-5I 

41-03 

0-8100 

95-18 

96-80 

0-8800 

68-25 

75-43 

0-9500 

32-95 

39*35 

0-8125 

94-28 

96-18 

0-8825 

67-18 

74-43 

0-9525 

3I-38 

37-61 

0-8150 

93-39 

95-55 

0-8850 

66-09 

73-41 

o-955o 

29-79 

35-8i 

0-8175 

92-50 

94-92 

0-8875 

64-98 

72-39 

0-9575 

28-14 

33-89 

0-8200 

91-60 

94-28 

0-8900 

63-86 

71-34 

o  -9600 

26-44 

31-82 

0-8225 

90-70 

93-63 

0-8925 

62-76 

70-28 

0-9625 

24-66 

29-83 

0-8250 

89-80 

92-98 

0-8950 

61-65 

69-23 

0-9650 

22-89 

27-83 

0-8275 

88-88 

92-31 

0-8975 

60-52 

68-17 

0-9675 

21-14 

25-76 

0-8300 

87-97 

91-64 

o  -9000 

59-36 

67-09 

0-9700 

19-38 

23-67 

0-8325 

87-06 

90-97 

0-9025 

58-20 

65-97 

0-9725 

17-63 

21-54 

0-8350 

86-16 

90-29 

0-9050 

57-01 

64-82 

0-9750 

I5-85 

19-40 

0-8375 

85-23 

89-60 

0-9075 

55-82 

63-65 

0-9775 

14-03 

17-25 

0-8400 

84-29 

88-88 

0-9100 

54-64 

62-46 

o  -9800 

12-27 

15-12 

0-8425 

83-34 

88-13 

0-9125 

53-49 

61-27 

0-9825 

10  -60 

13-04 

0-8450 

82-39 

87-40 

$-9150 

52-31 

60-04 

0-9850 

8-94 

11-03 

0-8475 

81-44 

86-64 

0-9175 

51-10 

58-80 

0-9875 

7-32 

9-06 

0-8500 

80-47 

85-88 

0-9200 

49-84 

57-54 

o  -9900 

5-72 

7-i3 

0-8525 

79-50 

85-09 

0-9225 

48-54 

56-20 

0-9925 

4-18 

5-30 

0-8550 

78-51 

84-27 

0-9250 

47-20 

54-79 

0-9950 

3-01 

3-84 

0-8575 

77-50 

83-44 

0-9275 

45-84 

53-36 

0-9975 

i-39 

1-69 

0-8600 

76-50 

82-61 

0-9300 

44"49 

51-92 

I'OOOO 

O'OO 

O'OO 

0-8625 

75-50 

81-76 

0-9325 

43-15 

50-48 

5.  Solubility  in  Caustic  Soda  Solution. — 20  c.c.  of  the  alcohol  are 
mixed  in  a  100  c.c.  graduated  cylinder  with  40  c.c.  of  32%  sodium  hydroxide 
solution  (D  i -35)  and  left  for  an  hour,  the  volume  of  the  floating  insoluble 
portion  being  noted. 

6.  Determination  of  the  Acetone. — Messinger's  method  is  used,  the 
following  solutions  being  required  : 

(a)  80  grams  of  caustic  soda  (puriss.),  free  from  nitrites,  per  litre.1 

(b)  Approximately  10%  sulphuric  acid  solution,  100  grams  of  the  pure 
cone,  acid  being  made  up  to  a  litre  ;    10  c.c.  of  this  solution  should  more 
than  neutralise  10  c.c.  of  (a). 

(c)  Approximately  N/5-ioaine  solution,  obtained  by  dissolving  about 

1  10  c.c.  of  this  solution,  treated  with  0-1-0-2  gram  of  potassium  iodide  and  acidified 
with  hydrochloric  acid,  should  yield  no  free  iodine. 


METHYL  ALCOHOL  41 

25-5  grams  of  iodine  in  a  solution  of  50  grams  of  potassium  iodide  in  200 
c.c.  of  water  and  making  the  volume  up  to  I  litre. 

(d)  Approximately   N/io-sodium   thiosulphate   solution,    prepared   by 
dissolving  25  grams  of  the  pure  salt  to  i  litre. 

(e)  Fresh  starch  paste. 

TlTRATION  OF  THE  THIOSULPHATE   SOLUTION.      To  2O  C.C.  of  an  aqUCOUS 

solution  containing  3-863  grams  of  potassum  dichromate  per  litre  are  added 
10  c.c.  of  10%  potassium  iodide  solution  and  5  c.c.  of  hydrochloric  acid 
(D  i-io).  After  mixing,  100-150  c.c.  of  water  are  added  and  the  free  iodine 
titrated  with  the  thiosulphate  solution.  Towards  the  end  of  the  titration, 
a  little  starch  paste  is  added,  addition  of  the  thiosulphate  being  discon- 
tinued when  a  drop  of  the  latter  changes  the  greenish  blue  colour  to  pale 
green.  Since  20  c.c.  of  the  dichromate  solution  set  free  0-2  gram  of  iodine 
from  the  potassium  iodide,  the  amount  of  iodine  corresponding  with  i  c.c. 
of  the  thiosulphate  solution  may  be  readily  calculated. 

TITRATION  OF  THE  IODINE  SOLUTION.  10  c.c.  of  the  iodine  solution  are 
pipetted  into  a  dish  and  the  thiosulphate  solution  run  in  from  a  burette 
until  the  liquid  becomes  pale  yellow.  Starch  paste  is  then  added  and  the 
titration  continued  until  the  liquid  becomes  colourless.  The  amount  of 
iodine  in  10  c.c.  of  the  solution  is  found  by  multiplying  the  number  of  c.c. 
of  thiosulphate  used  by  its  iodine  equivalent. 

METHOD  OF  WORKING.  25  c.c.  of  the  alcohol *  are  introduced  into  a  litre 
flask  containing  about  500  c.c.  of  water  and  the  solution  made  up  to  volume. 
After  mixing,  10  c.c.  of  the  liquid  (corresponding  with  0-25  c.c.  of  the  methyl 
alcohol)  are  placed  in  a  300-400  c.c.  bottle  fitted  with  a  ground  stopper 
and  containing  10  c.c.  of  the  caustic  soda  solution  (a)  ;  after  mixing,  40 
c.c.  of  solution  (c)  are  added  from  a  burette.  The  closed  bottle  is  left  for 
an  hour  with  occasional  shaking,  after  which  10  c.c.  of  solution  (b)  are 
added  and  the  non-combined  iodine  titrated  with  the  sodium  thiosulphate 
solution  >  (d).  Subtraction  of  non-combined  iodine  from  the  amount 
contained  in  40  c.c.  of  the  iodine  solution  gives  the  amount  reacting.2 
If  the  latter  is  a  grams,  the  percentage  of  acetone  is  given  by  the 
formula, 

58-05  X  a 


761-52 


X  100. 


This  gives  the  number  of  grams  of  acetone  in  100  c.c.  of  the  methyl 
alcohol ;  multiplication  by  0-7966 — the  density  of  acetone  at  15° — then 
yields  the  percentage  of  acetone  by  volume. 

7.  Bromine  Absorption. — From  this  determination  the  quantity  of 
various  impurities,  principally  allyl  alcohol,  is  deduced.  The  reagents 
required  are  : 

(a)  A  solution  of  potassium  bromate  and  bromide,  prepared  thus  : 
Powdered  potassium  bromate  and  bromide  (puriss.)  are  dried  separately 
in  porcelain  dishes  for  2  hours  at  100°.  2-447  grams  of  the  bromate  and 

1  With  rectified  methyl  alcohol,  50-100  c.c.  are  taken  according  to  its  supposed 
acetone  content. 

z  Each  mol.  of  acetone  (58-05)  requires  6  atoms  of  iodine  (761*52). 


42  ALUMINIUM  ACETATE 

8-719  grams  of  the  bromide  are  dissolved  separately  in  water  and  the  two 
solutions  mixed  and  made  up  to  i  litre. 

(b)  i  volume  of  cone,  sulphuric  acid,  mixed  with  3  vols.  of  water 
and  cooled. 

The  procedure  is  as  follows  :  100  c.c.  of  solution  (a)  and  20  c.c.  of  solu- 
tion (b)  are  mixed  in  a  100  c.c.  flask  and  the  methyl  alcohol  run  in  slowly 
from  a  burette  until  the  liquid  appears  colourless,  the  determination  being 
made  in  daylight  and  not  in  artificial  light.  The  bromine  absorption  is 
expressed  by  indicating  the  number  of  c.c.  of  methyl  alcohol  used. 

8.  Esters. — -To  10  c.c.  of  the  methyl  alcohol  mixed  with  40  c.c.  of  water 
and  a  few  drops  of  phenolphthalein  solution  N/io-potassium  hydroxide 
solution  is  added  until  the  liquid  becomes  pale  pink.  The  liquid  is  then 
boiled  for  15  minutes  with  20  c.c.  of  N-caustic  soda  solution  and,  after 
cooling,  the  excess  of  alkali  is  titrated  with  N-sulphuric  acid.  Multiplica- 
tion of  the  number  of  c.c.  of  caustic  potash  absorbed  in  the  saponification 
by  0-74  gives  the  quantity  of  esters,  calculated  as  methyl  acetate,  in  100 

c.c.  of  the  alcohol. 

* 
#    * 

Methyl  alcohol  (puriss.)  is  a  colourless,  neutral  liquid,  with  a  pleasant  odour 
recalling  that  of  ethyl  alcohol,  and  shows  at  least  99°  on  the  alcoholometer  and 
contains  not  more  than  0-1%  of  acetone.  It  should  distil  within  0-5°  and  the 
sulphuric  acid  test  should  give  only  a  slightly  yellow  liquid.  It  should  not 
decolorise  permanganate  immediately  and  should  mix  in  all  proportions  with 
water  without  opalescence  and  should  mix  with  concentrated  caustic  soda  solu- 
tion without  becoming  coloured. 

Commercial  methyl  alcohol  (rectified,  white  methyl  alcohol)  is  colourless  or 
only  faintly  yellowish,  with  a  distinctive,  stinging  odour  (not  empyreumatic)  ; 
its  alcoholometric  strength  is  95-99°,  its  b.pt.  64-67°,  and  as  a  rule  it  contains 
1-3%  of  acetone  (some  qualities  used  as  solvents  contain  as  much  as  15-20%). 

Crude  methyl  alcohol  or  wood  spirit  is  a  yellowish  liquid  of  empyreumatic 
odour  and  burning  taste,  its  alcoholometric  strength  being  90-91°  ;  it  is  not 
completely  soluble  in  caustic  soda  solution  (15-20%  separates),  contains  15-25% 
of  acetone  and  distils  to  the  extent  of  90%  between  60°  and  75°.  The  impurities 
are  principally  acetone,  methyl  acetate,  allyl  alcohol,  ammonia  and  pyridine 
bases,  empyreumatic  products,  etc. 

Crude  methyl  alcohol  to  be  used  for  the  denaturation  of  alcohol  must  satisfy, 
in  different  countries,  definite  conditions  as  to  colour,  specific  gravity,  boiling 
point,  solubility  in  water  and  in  caustic  soda  solution,  acetone  content,  absorp- 
tion of  bromine  and  other  less  important  characters. 

ALUM— POTASSIUM    ALUMINIUM    SULPHATE 

A12(SO4)3,  K2SO4  +  24H2O  =  949-2 

Large,  colourless,  transparent  crystals,  which  slowly  effloresce  in  the 
air,  soluble  in  10  parts  of  water,  insoluble  in  alcohol.  It  is  usually  moder- 
ately pure  and  it  is  usually  sufficient  to  test  it  for  iron  and  free  sulphuric 
acid,  as  described  under  Aluminium  Sulphate. 

ALUMINIUM    ACETATE 

For  use  in  dyeing,  normal  aluminium  acetate,  A1(C2H3O2)3,  the  basic 
acetate  and  various  sulpho -acetates  are  sold,  mostly  in  solution. 

The  impurities  to  be  sought  in  these  products  are  lead,  zinc,  iron,  lime 


ALUMINIUM  SULPHATE  43 

and  alkali,  which  are  detected  and  determined  as  in  aluminium  sulphate 
(vide  infra).  The  value  depends  on  the  content  of  alumina,  acetic  acid 
and  sulphuric  acid  :  the  alumina  and  sulphuric  acid  are  determined  as 
in  aluminium  sulphate  and  the  acetic  acid  as  in  calcium  acetate  (q.v.). 

The  compositions  of  the  basic  acetates  and  sulpho-acetates  of  aluminium 
vary  considerably.  The  sulpho-acetate  should  preferably  contain  I  part 
of  SO3  per  2  parts  of  A12O3. 

The  various  aluminium  acetates  should  be  free  more  especially  from 
iron  and  zinc  (see  also  Aluminium  Sulphate). 


ALUMINIUM    SULPHATE 

A12(SO4)3  +  i8H2O  -  666-2 

This  exists  in  commerce  in  various  forms  :  white,  crystalline,  nacreous 
scales  ;  in  lumps  or  cubical  or  prismatic  cakes,  which  are  hard,  white  and 
opaque  ;  in  spongy,  anhydrous,  white  masses.  In  the  first  two  forms  it 
is  easily  and  completely  soluble  in  water  giving  an  acid  solution  ;  the 
anhydrous  form  dissolves  slowly  and  often  leaves  an  insoluble  residue  of 
basic  sulphate. 

The  most  frequent  impurities  are  small  quantities  of  iron  salts  and  free 
sulphuric  acid  (to  be  tested  for  more  especially  when  the  product  is  to  serve 
for  d)^eing  purposes),  insoluble  substances  (silica,  sand)  and  rarely  zinc, 
copper,  lead,  chromium,  titanium  and  arsenic. 

Analysis  consists  essentially  of  determinations  of  the  insoluble  matter, 
alumina,  free  and  total  sulphuric  acid  and  iron  and  is  carried  out  as  described 
below.  Tests  for  the  other  impurities  mentioned  above  are  made  by  the 
ordinary  methods. 

The  sample  to  be  analysed  is  powdered  rapidly  and  weighed  in  a  closed 
vessel. 

1.  Insoluble  Matter. — A  solution  of  20  grams  in  water  is  filtered 
through  a  filter  previously  dried  at   105°  and  weighed.     The  insoluble 
matter  is  thoroughly  washed,  dried  at  105°  and  weighed.     The  filtrate  is 
made  up  to  500  c.c.  and  used  for  the  following  determinations. 

2.  Alumina. — This  is  determined  in  50  c.c.  of  the  solution  (2  grams 
of  material)  by  precipitating  with  ammonia  and  weighing  as  A12O3 1 ;   the 
weight  found  is  diminished  by  that  of  the  Fe2O3  found  as  in  5  (below). 

3.  Total  Sulphuric  Acid. — This  is  determined  in  25  c.c.  of  the  solution 
(i  gram  of  material)   as  barium  sulphate.     I  part  of  BaSO4  —  0-34335 
part  of  SO3  =  0-4206  part  of  H2S04.     From  the  result  is  deducted  any 
free  acid  found  (4). 

From  the  relation  between  the  alumina  and  the  sulphuric  acid  is  calcu- 
lated the  basicity  of  the  product,  from  which  it  is  deduced  whether  the 
sulphate  is  normal  or  more  or  less  basic.  By  basicity  number  is  meant  the 

1  In  order  to  avoid  the  action  of  organic  substances,  which  may  occur  in  the  com- 
mercial sulphate,  Delage  (Ann.  de  chim.  analyt.,  1911,  p.  325)  recommends  the  addition 
of  a  few  drops  of  bromine  to  the  solution,  which  is  then  evaporated  to  dryness,  heated 
slightly  until  the  residue  is  completely  decolorised,  then  taken  up  in  water  and  pre- 
cipitated with  ammonia. 


44  ALUMINIUM  SULPHATE 

quotient  obtained  by  dividing  the  percentage  of  sulphuric  acid  (H2SO4) 
by  that  of  aluminium  (Al). 

4.  Free  Sulphuric  Acid. — According  to  Iwanow,1  25  c.c.  of  the  solu- 
tion (i  gram  of  substance)  are  heated  to  about  85°  with  25  c.c.  of  water 
in  a  100  c.c.  flask,  and  to  the  hot  liquid  are  added,  with  continual  shaking, 
12  c.c.  of  a  i  :  12  potassium  ferrocyanide  solution  and  then  20  c.c.  of  i  :  10 
barium  chloride  solution.     After  vigorous  shaking,  the  liquid  is  made  up 
to  volume,  0-25  c.c.  of  water  being  added  to  compensate  for  the  volume 
occupied  by  the  precipitate  ;   after  standing,  25  or  50  c.c.  of  the  clear  liquid 
are  titrated  with  N/io-alkali  in  presence  of  methyl  orange  2  ;    i  c.c.  N/io- 
alkali  =  0-0049  gram  H2SO4. 

5.  Iron  (Lunge  and  Keler's  colorimetric  method). — The  following  are 
required  : 

(a)  10%  potassium  thiocyanate  solution  ; 

(b)  pure  ether  ; 

(c)  8-634  grams  of  ferric  ammonium  sulphate  (iron  alum)  and  6  c.c. 
of  pure  cone,  sulphuric  acid  per  litre  ;    i  c.c.  of  this  solution  diluted  to  100 
c.c.  gives  a  solution  containing  o-oio  gram  of  iron  per  litre  ; 

(d)  pure  nitric  acid,  free  from  iron  ; 

(e)  C3dinders  with  ground  stoppers  and  of  exactly  equal  height  and 
diameter  (internal  and  external),  reading  from  o  to  25  c.c.  in  tenths  and 
having  a  space  of  at  least  5  c.c.  between  the  25  c.c.  mark  and  the  stopper. 

The  procedure  is  as  follows  :  25  c.c.  of  the  solution  of  the  sulphate  pre- 
pared as  in  (i)  (=i  gram  of  substance)  are  evaporated  on  a  steam-bath 
to  about  5  c.c.,  i  c.c.  of  nitric  acid  (d)  being  then  added  and  the  liquid 
heated  for  a  few  minutes,  allowed  to  cool  and  diluted  to  50  c.c.  (solution 
S)  ;  further  i  c.c.  of  the  same  nitric  acid  is  diluted  to  50  c.c.  (solution  N). 
Into  one  cylinder  (A)  are  poured  5  c.c.  of  solution  S,  and  into  another  (B) 
5  c.c.  of  solution  N  to  which  is  added  a  measured  volume  (say,  i  c.c.)  of 
the  diluted  ferric  solution  c  (=  o-ooooi  gram  Fe),  the  liquids  in  the  two 
cylinders  being  made  up  to  the  same  volume  with  water.  To  each  cylinder 
are  then  added  5  c.c.  of  thiocyanate  solution  a  and  loc.  c.  of  ether,  the  cylin- 
ders being  next  closed  and  shaken  until  the  aqueous  layers  are  decolorised. 
A  comparison  is  then  made  of  the  intensity  of  colour  of  the  ethereal  layers 
in  the  two  cylinders  (if  the  coloration  is  light,  the  comparison  is  made  after 
some  hours  of  rest).  This  process  is  repeated  with  different  volumes  of 
the  iron  alum  solution  until  the  colours  of  the  two  ethereal  layers  match 
exactly  ;  o-i  c.c.  of  the  ferric  solution  should  produce  an  appreciable  differ- 
ence in  colour  intensity.- 

This  process  is  applicable  to  sulphates  containing  less  than  0-25%  Fe  ; 
with  larger  proportions,  a  more  dilute  solution  must  be  used. 

* 
*   * 

Pure  aluminium  sulphate,  A12(SO4)3  +  i8H2O,  contains  i5'33%  of  A12O3 

1  Chem.  Zeit.,   1913,  pp.  805  and  814. 

2  The  ferrocyanide  precipitates  all  the  aluminium  salt  and  the  free  sulphuric  acid 
remains  in  the  solution  ;    the  barium  chloride  then  precipitates  the  excess  of  ferro- 
cyanide and  the  free  sulphuric  acid,  but  liberates  hydrochloric  acid  equivalent  to  the 
latter. 


AMMONIA  45 

or  8-13%  Al,  44-4%  H2SO4  and  48-64%  of  water,  its  index  of  basicity  being  5-45. 
With  the  simple  basic  sulphate,  A12(SO4)2(OH)2,  the  index  of  basicity  is  3-62 
and  with  A18(SO4)(OH)4,  1-81. 

Commercial  sulphates  of  good  quality  should  not  contain  more  than  i% 
of  insoluble  matter,  and  their  content  of  iron  is  usually  very  small  (0-0002- 
0-005%).  For  turkey-red  dyeing  their  iron  content  should  not  exceed  0-001%, 
whilst  for  cotton  printing  as  much  as  0-05%  is  allowed. 

The  free  sulphuric  acid  varies  usually  from  0-2  to  i%  and  is,  of  course,  absent 
from  the  basic  sulphates.  The  presence  of  zinc  is  always  harmful,  but  it  is 
seldom  found. 


AMMONIA 

NH3  =  17-03  (17) 

Ammonia  is  commonly  sold  in  aqueous  solution,  D  =  0-910,  containing 
25%  by  weight  of  NH3;  the  strongest  solution,  D=o'88o,  contains  about 
35 -8  %  NH3.  The  pure  solution  is  colourless  and  has  a  pure  ammonia 
smell,  whereas  the  technical  product  may  be  yellowish  and  has  a  more 
or  less  pronounced  empyreumatic  odour. 

Liquefied  ammonia  is  also  sold  and  is  prepared  by  liquefying  the  gas 
in  steel  cylinders.  It  contains  97-99%  of  NH3,  besides  water,  traces  of 
ammonium  salts  and  lubricating  oil  from  the  compressor. 

The  commonest  impurities  of  ammonia  solution  consist  of  chlorides, 
sulphates,  carbonates,  copper,  lead,  iron,  zinc,  lime,  pyridine  bases  and 
tarry  products,  which  are  detected  as  below.  The  ammonia  content  is 
determined  as  in  5. 

1.  Chlorides,  Sulphates. — 10-20  c.c.,  rendered  acid  with  dilute  nitric 
acid,  should  not  be  rendered  turbid  by  silver  nitrate  (chlorides)  or  by  barium 
chloride,  even  after  12  hours  (sulphates). 

2.  Carbonates. — 10  c.c.,  mixed  with  30  c.c.  of  lime  water,  should  not 
become  turbid. 

3.  Metals. — 10  c.c.,  diluted  with  40  c.c.  of  water,  should  not  be  ren- 
dered coloured  or  turbid  by  hydrogen  sulphide  (copper,  lead,  iron,  zinc) 
or  ammonium  oxalate  (calcium). 

20  c.c.  should  leave  no  appreciable  residue  on  evaporation. 

4.  Pyridine  Bases,  Tarry  Products. — -These  may  be  detected  by 
the  smell,  especially  after  exact  neutralisation  of  .the  ammonia  with  dilute 
sulphuric  acid. 

10  c.c.,  rendered  acid  with  20  c.c.  of  pure  i  :  3  sulphuric  acid  (which 
does  not  decolorise  permanganate),  should  be  persistently  coloured  by  I 
drop  of  decinormal  permanganate. 

2  c.c.,  added  to  4  c.c.  of  nitric  acid,  should  give  a  colourless  liquid  leaving 
a  white  residue  on  evaporation  on  a  steam-bath. 

5.  Quantitative    Determination    of   the    NH3. — The   proportion    of 
ammonia  in  the  solution  may  be  found  from  the  specific  gravity  or  by 
titration  with  a  normal  acid  in  presence  of  methyl  orange  (i  c.c.  N-acid 
=  0-017  gram  NH3). 


46  AMMONIUM  CHLORIDE 

AMMONIUM    CARBONATE 

The  commercial  product  must  be  regarded  as  a  mixture  of  ammonium 
bicarbonate  and  carbamate,  NH4HCO3  +  NH4'CO2'NH2  =  157  (32-5% 
NH3).  It  forms  white,  fibrous,  crystalline  masses,  emitting  an  odour  of 
ammonia  and  is  slowly  soluble  in  4-5  parts  of  water  at  the  ordinary 
temperature. 

It  may  contain  small  quantities  of  chlorides,  sulphates,  tarry  matters 
and  fixed  substances. 

1.  Chlorides,  Sulphates. — -A  solution  of  i  gram  in  10  c.c.  of  dilute 
nitric  acid  should  not   be  rendered  turbid  by  silver  nitrate  or  barium 
chloride. 

2.  Tarry  Matters. — 2  grams  should  give  a  colourless  solution  with 
nitric  acid  and  the  solution  leave  a  white  residue  on  evaporation. 

3.  Volatility. — 10  grams  should  leave  no  appreciable    residue  when 
heated. 

4.  Determination  of  the  Ammonia. — This  is  made  by  distillation 
as  described  for  fertilisers  or  by  direct  titration  of  a  solution  of  the  carbonate 
with  a  normal  acid  in  presence  of  methyl  orange  ;    i  c.c.  N-acid  =  0-017 
gram  NH3. 

Commercial  ammonium  carbonate  contains  about  31%  NH3. 

AMMONIUM    CHLORIDE 

NH4C1  =  53-47  (53-5) 

This  is  put  on  the  market  in  lumps  or  crystalline  powder,  the  pure  being 
white  and  that  for  industrial  purposes  grey  or  yellowish.  It  may  contain 
as  impurities,  sulphates,  phosphates,  thiocyanates,  iron,  lead,  and  empyreu- 
matic  matters. 

1.  Volatility. — 10  grams  are  heated  until  all  white  fumes  disappear, 
any  residue  being  tested  for  heavy  metals,  alkalies  and  alkaline  earths. 

2.  Sulphates. — The  i  :  10  solution  is  treated  with  barium  chloride. 

3.  Phosphates. — 4  grams,    dissolved  in   40   c.c.   of   5%  magnesium 
chloride  solution  and  treated  with  6  c.c.  of  ammonia,  should  not  become 
turbid,  even  after  12  hours. 

4.  Thiocyanates. — The    i  :  10   solution,    acidified   with    hydrochloric 
acid,  is  tested  with  ferric  chloride. 

5.  Iron. — The  i  :  10  solution,  acidified  with  hydrochloric  acid,  is  tested 
with  potassium  ferrocyanide.     Quantitative  determination  may  be  carried 
out  as  in  aluminium  sulphate  (q.v.). 

6.  Empyreumatic  and  Tarry  Matters. — 2  grams,  moistened  with  a 
little  nitric  acid,  are  heated  to  dryness  on  a  steam-bath  :   in  presence  of 
tarry  products  a  yellowish  residue  remains,  the  residue  otherwise  being 
white. 

7.  Quantitative  Determination. — The  chlorine  is  estimated  volumetri- 
cally  by  Volhard's  method  (see  Potable  Waters)  and  the  ammonia  by  dis- 
tillation with  sodium  hydroxide  (see  Fertilisers). 


AMMONIUM  THIOCYANATE  47 

AMMONIUM    PERSULPHATE 

NH4SO4  =  114 

Colourless  crystals,  alterable  in  moist  air,  soluble  in  water.  The  aqueous 
solution  decomposes  slowly  with  evolution  of  oxygen,  and  rapidly  when 
heated  with  an  acid  ;  it  decomposes  potassium  iodide  solution,  liberating 
iodine.  It  always  contains  more  or  less  marked  quantities  of  ammonium 
bisulphate,  moisture,  and  alkali,  its  value  depending  on  its  content  of  the 
persulphate. 

1.  Determination  of  the  Persulphate  (Ulzer's  method). — 0-3  gram 
is  dissolved  in  about  100  c.c.  of  water  in  a  flask  with  a  stopper  fitted  with 
a  Bunsen  valve  and  the  liquid  boiled  for  about  30 'minutes  with  excess  of 
ferrous  ammonium  sulphate  (1-1-5  gram)  and  dilute  sulphuric  acid.     The 
excess  of  ferrous  salt  is  then  titrated  with  standard  permanganate  (i  c.c. 
N/io-permanganate  =  0-0114  gram  of  NH4S04). 

The  persulphate  may  also  be  determined  iodometrically.  According 
to  Mondolfo,  2-3  grams  of  the  persulphate  are  dissolved  in  100  c.c.  of  cold 
water  and  10  c.c.  of  the  solution  heated  for  10  minutes  in  an  oven  at  60-80° 
with  an  excess  (0-25-0-5  gram)  of  potassium  iodide  (puriss.)  in  a  small 
bottle  with  a  ground  stopper.  The  iodine  liberated  is  titrated  with  N/io- 
thiosulphate  and  starch  paste  (i  c.c.  N/io-thiosulphate  =  0-0114  gram 
NH4S04). 

From  the  amount  of  persulphate  present,  the  active  oxygen  which  a 
commercial  persulphate  can  furnish  may  be  calculated,  knowing  that  i 
part  of  NH4S04  =  0-07  part  of  oxygen. 

2.  Other   Determinations. — Complete   analysis   includes   determina- 
tions of  :   (a)  the  total  sulphuric  acid,  by  precipitation  with  barium  chloride 
after  the  persulphate  solution  has  been  boiled  with  hydrochloric  acid  until 
the  persulphate  is  completely  decomposed  ;    (b)  the  total  ammonia,  by  one 
of  the  ordinary  methods  (see  Fertilisers)  ;    (c)  the  acidity,  by  titrating  a 
solution  of  the  persulphate,  made  in  the  cold,  with  N-alkali  and  methyl 
orange  ;    (d)  the  fixed  residue  after  calcination.     From  the  total  sulphuric 
acid  is  subtracted  that  combined  with  the  ammonia  as  persulphate  (i)  and 
from  the  total  ammonia  that  in  the  form  of  persulphate ;   if  sulphuric  acid 
and  ammonia  remain,  they  are  regarded  as  existing  as  ammonium  bisulphate. 

In  the  same  way  potassium  persulphate,  KSO4  =  135-1,  is  analysed. 

AMMONIUM    SULPHATE 

(See  Fertilisers) 

AMMONIUM    THIOGYANATE 
(Ammonium  Sulphocyanide) 

NH4CSN  =  76 

Colourless,  deliquescent  crystals,  extremely  soluble  in  water  or  alcohol. 
Its  analysis  includes  tests  for  certain  impurities  (sulphates,  iron,  lead)  and 
determinations  of  the  proportions  of  thiocyanic  acid  and  ammonia. 


48  AMYL  ACETATE 

1.  Solubility. — i  gram  should  give  a  clear  solution  with  10  c.c.  of 
absolute  alcohol. 

2.  Volatility. — 2  grams  should  volatilise  without  leaving  appreciable 
residue  when  heated  in  a  platinum  crucible. 

3.  Sulphates. — The  i  :  20  solution,  when  treated  with  barium  chloride 
solution,  should  remain  clear  at  least  5  minutes. 

4.  Metals.— The  i  :  20  solution  should  not  change  with  ammonium 
sulphide  (lead,  iron,  etc.)  and,  when  acidified  with  dilute  hydrochloric  acid, 
should  remain  colourless  (iron). 

5.  Thiocyanic  Acid. — TO  grams  are  dissolved  in  water  and  the  solu- 
tion made  up  to  500  c.c.     To  5  c.c.  of  the  solution  (=  o-i  gram  of  substance) 
are  added  20  c.c.    of  "N/io-sirver  nitrate,  the  liquid  being  acidified  with 
nitric  acid  and  a  few  drops  of  saturated  ferric  alum  solution  added  ;    the 
excess  of  silver  nitrate  is  then  titrated  with  N/io-potassium  thiocyanate 
solution  until  a  reddish  coloration  appears.     The  difference  between  the 
20  c.c.  of  silver  nitrate  and  the  number  of  c.c.  of  thiocyanate,  multiplied 
by  5-9,  gives  percentage  of  HCNS,  and  multiplied  by  5-8,  percentage  of  CNS. 

6.  Ammonia. — This    is    determined    by    distillation    (see   Fertilisers) 
with  magnesium  oxide  instead  of  sodium  hydroxide. 

Chemically  pure  ammonium  thiocyanate  contains  77-63%  of  HCNS  and 
22>37%  °f  NH3  ;  the  commercial  pure  product,  which  should  be  perfectly  white 
and  odourless,  almost  always  contains  traces  of  lead,  iron,  and  moisture.  It 
occurs  also  in  a  yellowish  form  with  an  empyreumatic  odour  and  contaminated 
with  marked  proportions  of  sulphate. 


AMMONIUM    VANADATE 

NH4VO3  =  117 

White  or  faintly  yellow  crystalline  powder,  soluble  in  water.  The 
purity  and  value  are  deduced  from  the  determination  of  the  vanadic  acid. 

Determination  of  the  Vanadic  Acid. — 1-2  grams,  dissolved  in  very 
little  water,  are  treated  in  the  hot  with  excess  of  saturated  ammonium 
chloride  solution,  in  which  ammonium  vanadate  is  insoluble  ;  after  48  hours, 
the  liquid  is  filtered  and  the  precipitate  washed  with  saturated  ammonium 
chloride  solution  and  then  with  about  50%  alcohol.  After  being  dried  at 
100°,  the  precipitate  is  detached  as  well  as  possible  from  the  filter,  the  latter 
being  burned  separately,  its  ash  moistened  with  nitric  acid  and  again  cal- 
cined ;  the  precipitate  is  then  added  and  the  whole  calcined  and  the  vanadic 
anhydride  weighed,  i  part  V2O5  =  1-286  part  NH4VO3. 

AMYL    ACETATE 

CBHu-CaH,O8  =  130 

Colourless,  neutral  liquid  of  pleasant,  ethereal  odour,  D  =  0-875  at 
15°,  b.pt.  138-139°,  very  slightly  soluble  in  wrater  but  readily  in  alcohol 
or  ether.  It  may  be  contaminated  with  amyl,  ethyl,  propyl  and  butyl 
alcohols  and  their  acetic  esters  and  by  acetic,  sulphuric  and  hydrochloric 


AMYL  ACETATE  49 

acids.     It  is  adulterated  with  ethyl  acetate,  acetone,  benzene  and  mineral 
oils.     Its  analysis  includes  the  following  tests  and  determinations.1 

1.  Specific   Gravity. — This  is  measured  by  Mohr's  balance  or  the 
picnometer  at  15°.    The  presence  of  amyl,  ethyl,  propyl  alcohols,  etc.,  acetone 
or  mineral  oil  lowers  the  specific  gravity,  whilst  that  of  ethyl,  or  propyl 
acetate,  etc.,  or  benzene  raises  it. 

2.  Boiling   Point. — 100  c.c.  are  distilled  from  a  flask  furnished  with 
a  thermometer,  the  different  fractions  distilling  up  to  100°,  100-110°,  etc., 
being  collected.     With  the  exception  of  the  mineral  oils  (150-170°),  the 
various  impurities  and  adulterants  mostly  boil  at  lower  temperatures  than 
pure  amyl  acetate  (138°). 

3.  Non -volatile   Substances. — -20  c.c.   are  evaporated  slowly  on   a 
steam-bath  and  any  weighable  residue  determined.      Further,  a  drop  is 
evaporated  on  a  filter-paper  and  any  residual  oily  spot  observed. 

4.  Solubility. — i  c.c.  is  shaken  with  an  equal  volume  of  benzene  or 
carbon  disulphide  or  with  10  c.c.  of  90%  alcohol  and  10  c.c.  of  water  and 
note  taken  if  a  limpid  solution  is  formed  with  each  of  these  solvents. 

5.  Free  Acids. — 10  c.c.   are  shaken  with  as  much  water  and,  after 
standing,  the  aqueous  liquid  separated  and  tested  with  litmus  paper  ;    or 
the  aqueous  solution  is  acidified  with  dilute  nitric  acid  and  tested  with 
barium  chloride  (sulphuric  acid)  and  with  silver  nitrate  (hydrochloric  acid}. 

6.  Alcohol  and  Acetone. — 10  c.c.  are  shaken  with  an  equal  volume 
of  saturated  calcium  chloride  and,  after  standing,  any  diminution  in  the 
volume  of  the  acetate  observed  (in  a  graduated  cylinder  any  diminution 
may  be  measured  approximately).     The  aqueous  liquid  is  separated  and 
distilled,  the  distillate  being  tested  for  ethyl  alcohol  (see  Amyl  Alcohol) 
and  acetone  (see  Methyl  Alcohol). 

If  the  proportion  of  ethyl  alcohol  is  required,  50  c.c.  of  the  amyl  acetate 
are  shaken  with  100  c.c.  of  calcium  chloride  solution  of  D  =  1-25  and  30 
c.c.  of  pure  cumene.  After  standing,  the  aqueous  liquid  is  separated  and 
the  supernatant  amylic  liquid  treated  with  two  further  quantities  of  50 
c.c.  of  the  calcium  chloride  solution.  The  aqueous  liquids  are  then  united 
and  distilled  until  50  c.c.  is  collected,  this  being  filtered  through  a  dry 
paper  and  the  alcohol  content  determined  by  means  of  the  specific  gravity. 
It  is,  of  course,  necessary  that  the  product  examined  shall  be  free  from 
acetone  and  other  liquids  soluble  in  water. 

7.  Ethyl  Acetate. — 10  c.c.  are  boiled  for  30  minutes  in  a  reflux  apparatus 
with  50  c.c.  of  a  15%  solution  of  potassium  hydroxide  in  amyl  alcohol.     The 
liquid  is  then  distilled  and  the  first  1-2  c.c.  collected  shaken  with  water 
and  the  aqueous  liquid  tested  for  ethyl  alcohol. 

For  the  quantitative  determination,  50  c.c.  of  the  substance  and  25-30 
grams  of  caustic  potash  dissolved  in  50  c.c.  of  amyl  alcohol  are  taken  and 
50  c.c.  distilled  over.  The  distillate  is  then  treated  as  indicated  in  section 
6  for  the  determination  of  the  alcohol.  The  alcohol  by  volume  multiplied 
by  1-508  gives  the  weight  of  ethyl  acetate  in  100  c.c.  of  the  amyl  acetate 
tested. 

1  For  the  analysis  of  amyl  acetate  see  also  article  by  Chercheffski  in  Les  matures 
grasses,  1913,  p.  3103. 

A.C.  4 


50  ANILINE 

8.  Benzene  and  Mineral  Oils.— 2-3  c.c.  are  shaken  in  a  test-tube 
with  as  much  pure  sulphuric  acid  (66°  Baume)  ;    after  5-10  minutes  the 
appearance  of  a  turbidity  indicates  benzene  or  the  separation  at  the  surface 
of  drops  or  a  liquid  layer,  mineral  oils. 

9.  Determination  of  the  Amyl  Acetate/ — This  is  effected  by  means 
of  the  saponification  number,  proceeding  as  with  essential  oils  (q.v.).     The 
saponification  number  of  pure  amyl  acetate  is  431  ;    i  part  of  KOH  = 
2-3169  parts  of  CgHn'CaHsOa. 

Ethyl,  propyl  and  butyl  acetates,  having  the  respective  saponincation 
indices,  636,  549  and  483,  raise  that  of  amyl  acetate,  whilst  alcohols  (amyl, 
ethyl),  acetone,  benzene  and  mineral  oils  lower  it. 

Commercial  amyl  acetate  almost  always  contains  a  certain  proportion  of 
free  amyl  alcohol.  It  may  be  regarded  as  technically  pure  (e.g.,  when  required 
for  photometric  purposes)  when  it  has  D  =  0-872  -  0-876,  distils  to  the  extent 
°f  9°%  between  137°  and  143°,  has  a  saponincation  number  of  about  430,  is 
neutral  and  leaves  no  oily  spot  on  filter-paper. 

ANILINE 

C6H6-NH2  =  93 

Various  qualities  of  aniline  are  found  on  the  market  :  Pure  aniline 
(aniline  oil  for  blue],  a  colourless  or  yellowish  liquid  which  readily  turns 
brown  in  the  air  and  light,  and  has  an  aromatic  odour.  Aniline  oils  (crude 
anilines),  mixtures  of  aniline  with  ortho-  and  para-toluidines,  form  reddish- 
brown  liquids  of  unpleasant  odour.  Aniline  oil  for  red  contains  about  equal 
proportions  of  aniline,  ortho-  and  para-toluidine,  and  aniline  oil  for  safranine 
about  40%  of  aniline  and  60%  of  orthotoluidine.  Liquid  toluidine  is  a 
mixture  of  ortho-  and  para-toluidines  with  a  little  aniline. 

1 .    Aniline 

With  aniline,  besides  determinations  of  the  specific  gravity  and  boiling 
point  by  the  ordinary  methods,  the  following  tests  are  made  : 

1.  Non-basic  Substances. — 10  c.c.  should  give  a  quite  clear  solution 
with  50  c.c.  of  water  and  40  c.c.  of  hydrochloric  acid  ;  incomplete  solution 
indicates  the  presence  of  hydrocarbons  and  nitrobenzene. 

2.  Moisture. — 100  c.c.  are  distilled,  the  first  10  c.c.  of  distillate  being 
collected  in  a  graduated  15  c.c.  cylinder  and  shaken  with  i  c.c.  of  saturated 
sodium  chloride  solution  and  any  diminution  in  its  volume  noted. 

3.  Sulphur. — 100  c.c.  are  boiled  for  some  time  in  a  reflux  apparatus 
(the  sulphur  being  transformed  into  hydrogen  sulphide)  and  a  current  of 
carbon  dioxide  then  passed  through  the  aniline  into  silver  nitrate  solution  ; 
a  black  precipitate  in  the  latter  indicates  that  the  aniline  contains  sulphur. 
This  test  is  quantitative  when  standard  silver  nitrate  solution  is  used  and 
the  titre  determined  after  removal  of  the  sulphide  by  filtration. 

4.  Determination  of  the  Aniline. —  If  the  preceding  tests  indicate 
that  the  aniline  is  not  pure,  the  aniline  may  be  determined  by  the  method 
described  below  for  aniline  oils. 

Pure  aniline  has  D  1-0267  at  15°  and  b.pt.  184°.     The  commercial  pure  pro- 


ANILINE  51 

duct  should  have  D  1-0265-1-0267  and  from  87  to  98%  of  it  should  distil  within 
1-1-5°  ;   it  should  contain  only  traces  of  moisture  and  impurities. 

2.    Aniline  Oils 

With  aniline  oils,  besides  the  above  determinations,  the  proportions  of 
the  various  bases  present,  namely,  aniline  and  o-  and  p-toluidines  are  deter- 
mined. The  estimation  may  be  made  by  Reinhardt's  method,1  which  is 
based  on  the  fact  that,  with  a  mixture  of  potassium  bromide  and  bromate, 
aniline  in  acid  solution  is  transformed  into  tribromoaniline,  whereas  o-  and 
p-toluidines  give  dibromo-compounds,  and  that  by  oxalic  acid  in  acid 
solution,  p-toluidine  and  aniline  are  precipitated  whilst  o-toluidine  remains 
in  solution.  The  procedure  is  as  follows  : 

(a)  DETERMINATION  OF  THE  ANILINE  AND  OF  THE  TWO  TOLUIDINES  TO- 
GETHER. The  brominating  mixture  is  prepared  from  490  grams  of  bromine, 
336  of  caustic  potash  and  i  litre  of  water  ;  the  liquid  is  boiled  gently  for 
2-3  hours  and  diluted  to  9  litres  (it  should  be  free  from  hypobromite).2 
To  1-5-2  grams  of  pure  aniline  are  added  100  c.c.  of  hydrobromic  acid  of 
D  =  1-45-1-48  (or  the  corresponding  quantities  of  KBr  and  HC1),  the 
liquid  being  diluted  with  a  litre  of  water  and  the  above  brominating  solu- 
tion added  from  a  burette  until  a  drop  of  the  liquid  colours  a  starch-iodide 
paper  blue.  Division  of  the  amount  of  aniline  taken  by  the  number  of  c.c. 
of  the  brominating  solution  required  gives  the  quantity  of  aniline  (t)  corre- 
sponding with  each  c.c.  of  the  brominating  solution.3  From  i-  to  2  grams 
of  the  aniline  oil  are  then  titrated  in  the  same  way,  the  content  in  aniline 
(x)  being  calculated  from  the  formulae  : 

x  =  2-3777  v  i  — 1-3777  «, 
so  that  the  percentage  (p)  of  aniline  will  be 

x  .100 
p—-     —. 

a 

where  a  =  quantity  of  substance  taken. 
x  =  aniline  content  in  a. 
v  =  c.c.  of  brominating  solution  used  in  test. 
t  =  titre  in  aniline  of  the  brominating  solution. 
The  percentage  of  the  two  toluidines  together  in  the  oil  will  be 

100  —  p. 

(b)  DETERMINATION  OF  P-TOLUIDINE  WHEN  MIXED  WITH  EITHER  ANILINE 
OR  O-TOLUIDINE  OR  WITH  BOTH  BASES.  ioo  grams  of  the  oil  are  dissolved 
in  106  grams  of  31%  hydrochloric  acid  (D  1-163)  ar*d  the  liquid  poured  into 
a  boiling  10%  solution  of  pure  oxalic  acid  ;  4  the  liquid  should  remain 

1  Chem.  Zeit.,   1893,  p,  413. 

2  An  approximately  N/j-solution  of  recrystallised  potassium  bromate  may  also  be 
used. 

3  This  titre  remains  moderately  constant. 

*  The  quantity  of  oxalic  acid  should  be  greater  than  that  necessary  to  precipitate 
all  the  p-toluidine  present,  which  may  be  established  by  a  preliminary  experiment. 
For  oils  poor  in  aniline,  about  10  grams  of  oxalic  acid  more  than  is  necessary  should  be 
used,  and  for  those  richer  about  20  grams  more.  In  general,  50  grams  of  oxalic  acid 
in  500  c,c.  of  water  may  be  used  for  ioo  grams  of  oil. 


52  ANTIMONY  AND   POTASSIUM  TARTRA  TE  (TARTAR  EMETIC) 

clear.  During  cooling  the  liquid  is  frequently  shaken  and  after  standing 
for  48  hours  is  filtered  to  separate  the  oxalates,  which  are  washed  with  3 
quantities  of  25  c.c.  of  water  and  are  then  treated  with  boiling  potassium 
hydroxide  solution  (100  c.c.  of  potassium  hydroxide  solution  of  45°  Baume 
and  200  c.c.  of  water).  In  this  way  the  oxalates  are  decomposed,  and 
after  cooling  the  bases  (aniline  and  p-toluidine)  are  separated  and  weighed, 
the  o-toluidine  being  then  determined  by  difference.  If  the  aniline  is  deter- 
mined, as  in  (a],  in  the  mixture  of  bases  separated  from  the  oxalates  and 
dried  with  potash,  the  proportion  of  aniline  and  hence  that  of  p-toluidine 
in  the  oil  are  known. 

Aniline  oil  for  red  has  D  =  1-006-1-009  at  15°,  distils  almost  completely 
between  182°  and  198°  and  is  almost  entirely  soluble  in  dilute  hydrochloric 
acid.  That  for  safranine  has  D  =  1-032-1-034  and  often  contains  consider- 
able quantities  of  non-basic  products,  so  that  it  gives  a  very  turbid  solution 
with  dilute  hydrochloric  acid  ;  it  contains  as  a  rule  4-6%  and  sometimes  12% 
of  p-toluidine. 

3.    Liquid  Toluidine 

The  determinations  to  be  made  are  the  same  as  with  aniline  oils.  Accord- 
ing to  Lunge  x  the  density  may  be  used  to  deduce  the  proportions  of  o-  and 
p-toluidines,  when  aniline  and  other  substances  are  absent. 

o-  and  p-Toluidines  are  also  sold  in  a  fairly  pure  form.  The  former  is  a  liquid, 
D  =  1-0037  at  15°,  b.pt.  198°  and  the  second  solid,  D  =  1-046,  m.pt.  45°,  b.pt. 
198°. 

ANTIMONY    AND    POTASSIUM    TARTRATE 
(Tartar  Emetic) 

K(SbO)C4H406  +  iH20  =  332-3 

Colourless,  transparent  crystals,  which  readily  effloresce,  becoming 
opaque,  irregular  pieces  or  crystalline  powder.  It  dissolves  in  17  parts 
of  cold  water  with  a  faintly  acid  reaction,  but  is  insoluble  in  alcohol.  It 
may  be  impure  with  cream  of  tartar,  calcium  salts,  sulphates,  chlorides, 
antimony  and  potassium  oxalate,  iron,  zinc,  copper,  lead  and  arsenic.  The 
various  tests  to  be  made  are  as  follows  : 

1.  Solubility. — A  clear  solution  should  be  obtained  with  0-5  gram  and 
8-10  c.c.  of  cold  water  or  i  c.c.  of  boiling  water ;    any    insoluble  residue 
indicates  cream  of  tartar  or  calcium  salts. 

2.  Sulphates,  Chlorides,  Oxalates,  Lime. — 4  grams  are  dissolved 
in  80  c.c.  of  water  acidified  with  tartaric  acid  and  four  portions  of  the  solu- 
tion tested  respectively  with  barium  chloride,  silver  nitrate,  calcium  chloride 
and  ammonium  oxalate. 

3.  Arsenic. — -0-5  gram,  dissolved  in  a  little  cone,  hydrochloric  acid 
and  treated  with  5  c.c.  of  Bettendorf's  reagent,  should  not  colour  within 
an  hour. 

4.  Metals. — -i  gram,  dissolved  in  20  c.c.  of  water  and  sodium  hydroxide 
solution  added  until  the  precipitate  formed  redissolves  and  then  saturated 

1  Chem.  Ind.,   1885,  VIII,  p.  74. 


BARIUM  PEROXIDE  53 

with  hydrogen  sulphide,  should  not  give  a  brown  (iron,  copper,  lead]  or 
white  turbidity  (zinc}. 

5.  Determination  of  the  Antimony.- — 0-5  gram  is  dissolved  in  50  c.c, 
of  water  and  10%  sodium  bicarbonate  solution  added  to  give  an  alkaline 
reaction ;  should  a  little  precipitate  form,  it  is  removed  by  addition  of  a 
little  Rochelle  salt  dissolved  in  water.  Starch  paste  is  added  and  the 
liquid  titrated  with  N/io-iodine  until  a  blue  colour,  persisting  for  a  short 
time,  is  obtained,  i  c.c.  N/io-iodine  =  0-00721  gram  Sb2O3  =  0-00601 

gram  Sb. 

• 
*   * 

Chemically  pure  tartar  emetic  contains  43-4%  Sb2O3,  and  the  commercial 
products  usually  contain  42-43%.  For  use  in  dyeing  it  should  be  free  especially 
from  iron,  whilst  for  medicinal  purposes  it  should  contain  none  of  the  above 
impurities  and  should  hence  answer  all  the  tests  1-4. 

As  substitutes  for  tartar  emetic  in  dyeing,  various  other  antimony  com- 
pounds are  used,  such  as  double  oxalates  and  fluorides  of  antimony  and  potassium 
or  sodium  and  ammonium,  or  lactates  of  antimony  and  sodium  or  calcium  (anti- 
monin).  In  these  products  the  antimony  is  determined  as  in  5  (above),  and 
the  test  for  iron  made. 

BARIUM    CHLORIDE 

Bad  2  +  2H2O  =  244-29 

Colourless  crystals,  soluble  in  water,  insoluble  in  cone,  hydrochloric 
acid.  The  commercial  salt  for  technical  uses  may  be  yellowish  or  greyish 
and  in  fine  powder  (flour). 

It  may  contain,  as  impurities,  iron,  calcium  chloride  (hygroscopic) 
and  potassium  chloride  (sometimes  large  quantities).  In  general,  the 
following  tests  are  sufficient  : 

1.  Solubility,  Heavy  Metals. — i  gram,  dissolved  in  10  c.c.  of  water, 
should  give  a  clear,  neutral  solution  which,  when  acidified  with  hydrochloric 
acid,  is  not  altered  by  potassium  ferrocyanide  (iron)  or  hydrogen  sulphide, 
even  after  being  made  alkaline  with  ammonia  (other  metals}. 

2.  Lime  and  Alkalies. — 5  grams,  dissolved  in  50  c.c.  of  water,  are 
precipitated  in  the  hot  by  dilute  sulphuric  acid  and  filtered  :    the  filtrate 
should  not  be  rendered  turbid  by  alcohol  and,  when  evaporated  to  dryness 
and  ignited,  it  should  leave  no  appreciable  residue. 

BARIUM    PEROXIDE 

BaO2  =  169-37  (169) 

White  or  greyish  powder,  insoluble  in  water  ;  with  dilute  sulphuric  acid 
it  gives  hydrogen  peroxide. 

Its  value  depends  essentially  on  the  proportion  of  BaO2,  which  is  deter- 
mined in  the  following  way  :  0-2-0-3  gram  is  introduced,  gradually  and 
with  shaking,  into  300  c.c.  of  10%  sulphuric  acid,  the  hydrogen  peroxide 
thus  formed  being  titrated  with  N/5-permanganate  solution  ;  i  c.c.  N/5- 
permanganate  =  0-0169  gram  Ba02. 

Commercial  barium  peroxide  usually  contains  80-85%  °f  BaO2,  the  remainder 
being  barium  oxide  and  a  few  other  impurities  ;  some  of  the  better  grades  con- 
tain, however,  90-91%  BaO2. 


54  BARYTA   (BARIUM  HYDROXIDE) 

BARYTA    (Barium  Hydroxide) 

Ba(OH)2  +  8H20  =  315-37 

Colourless,  more  or  less  opaque,  lamellar  crystals,  or  white  or  yellowish 
fused  masses  ;  in  the  crude  state  it  forms  more  or  less  grey  crystalline 
masses.  It  dissolves  in  20  parts  of  cold,  or  2  parts  of  boiling  water,  but 
complete  solution  is  difficult  owing  to  the  presence  of  insoluble  carbonate. 
Its  impurities  may  be  carbonate,  sulphate,  sulphide  and  thiosulphate  of 
barium,  chlorides,  heavy,  earthy  and  alkali  metals.  Its  examination 
includes  : 

1.  Carbonate,  Sulphate. — 2-3  grams  are  dissolved  in  dilute  hydro- 
chloric acid,  effervescence  indicating  carbonate  in  considerable  amount  ; 
insoluble  residue  may  be  barium  sulphate. 

2.  Sulphide. — 5  grams  are  dissolved  in  excess  of  hydrochloric  acid 
and  the  solution  heated,  evolution  of  hydrogen  sulphide  being  tested  for 
with  lead  acetate  paper  ;  or,  a  few  drops  of  lead  acetate  solution  are  added 
to  the  aqueous  solution  and  any  black  precipitate  noted. 

3.  Sulphite,  Thiosulphate. — 5  grams  are  treated  with  50  c.c.  of  water 
and  about  0-5  gram  of  cadmium  carbonate    (to  eliminate  the  sulphide), 
the  liquid  being  heated  for  about  30  minutes  on  the  steam-bath  and  filtered. 
To  the  filtrate  are  added  a  little  starch  paste  and  then  dilute  iodine  solution  ; 
in  absence  of  sulphite  and  thiosulphate,  a  blue  coloration  appears  imme- 
diately. 

4.  Chlorides. — 2-3  grams,  dissolved  in  dilute  nitric  acid,  should  not 
be  rendered  turbid  by  silver  nitrate. 

5.  Heavy   Metals. — The  hydrochloric  acid  solution  is  treated  with 
hydrogen   sulphide  and  then   with  ammonia   and  ammonium  sulphide ; 
traces  of  lead  and  copper  and  small  proportions  of  iron  are  to  be  tested  for. 

6.  Alkaline  Earths,  Alkalies. — 5  grams  are  dissolved  in  dilute  hydro- 
chloric acid,  the  solution  heated  and  the  barium  precipitated  with  sulphuric 
acid  and  filtered.     The  filtrate  should  remain  clear  on  addition  of  alcohol 
and  should  leave  no  sensible  residue  on  evaporation  in  a  platinum  dish. 

7.  Quantitative   Determination. — 35-40   grams   of   the   baryta   are 
dissolved  in  boiled  water  and  the  volume  made  up  to  i  litre.     The  following 
determinations  are  made  on  aliquot  parts  of  this  solution  removed  by  means 
of  a  burette  with  automatic  filling  device,  in  order  to  avoid  the  action  of 
atmospheric  carbon  dioxide. 

(a)  Barium  hydroxide.     25  c.c.   of  N/5-hydrochloric  acid,  plus  about 
200  c.c.  of  water  and  10-12  drops  of  0-5%  methyl  orange  solution,  are 
titrated  with  the  baryta  solution,  the  point  of  neutrality  being  taken  as 
the  change  from  orange  yellow  to  a  distinct  yellow.     25  c.c.  N/5-HC1  = 
07885  gram  Ba(OH)2  +  8H2O. 

(b)  Hydrogen  sulphide  and  thiosulphuric  acid. 

(i)  200  c.c.  of  the  baryta  solution  are  acidified  with  acetic  acid  in  a  half- 
litre  bottle  with  a  ground  stopper,  a  little  starch  paste  being  then  added 
and  the  liquid  titrated  with  about  N/io-iodine  solution.  The  iodine  solu- 
tion is  previously  titrated  with  N/io-sodium  thiosulphate  solution. 


BLEACHING  POWDER  (CHLORIDE  OF  LIME)  55 

(2)  200  c.c.  of  the  baryta  solution  are  treated  in  a  250  c.c.  flask  with 
a  little  cadmium  carbonate  suspended  in  water  and  heated  for  about  30 
minutes  on  a  steam-bath  with  frequent  shaking.  On  cooling,  the  liquid 
is  made  up  to  250  c.c.  and  filtered  through  a  dry  paper,  200  c.c.  of  the  fil- 
trate, acidified  with  acetic  acid,  being  titrated  with  iodine  in  presence  of 
starch  paste. 

The  first  titration  gives  the  iodine  consumed  by  the  sulphides  and 
thiosulphates  and  the  second  that  consumed  by  the  thiosulphates  alone ; 
it  is  easy,  therefore,  to  deduce  the  thiosulphuric  acid  and  hydrogen  sulphide, 
which  are  calculated  as  barium  salts. 

(c)  Other  determinations.  Commercial  baryta  does  not  usually  contain 
lime  and  free  alkali  in  appreciable  quantity ;  otherwise  the  volumetric 
determination  of  the  baryta  gives  inaccurate  results. 

The  presence  of  other  bases  is  readily  detected  indirectly,  by  determining 
the  barium  in  25  c.c.  of  the  aqueous  solution — prepared  as  above — gravi- 
metrically  as  sulphate  and  calculating  it  as  crystallised  barium  hydroxide. 
If  this  result  is  lower  than  that  obtained  volumetrically,  the  latter  must 
be  erroneous  owing  to  the  presence  of  other  bases. 


BLEACHING    POWDER 
(Chloride  of  Lime) 

CaOCl2  =  127 

White,  hygroscopic  powder  with  an  odour  of  chlorine,  partially  soluble 
in  water  and  soluble  in  hydrochloric  acid  with  evolution  of  chlorine.  The 
commercial  value  depends  on  the  content  of  available  chlorine.  That  to 
be  used  for  bleaching  textiles  should  be  tested  for  iron  and  manganese. 

Determination  of  the  Available  Chlorine  (Penot  and  Lunge's 
method). — -10  grams  are  well  pounded  in  a  mortar  with  a  little  water,  further 
quantities  of  water  being  gradually  added  with  constant  mixing.  The 
whole  of  the  liquid  and  solid  matter  is  introduced  into  a  litre  measuring, 
flask  and  made  up  to  the  mark  and  mixed,  50  c.c.  of  the  turbid  liquid  being 
immediately  removed.  Into  this  liquid  standard  sodium  arsenite  1  is  run 
slowly  from  a  burette  with  gentle  shaking  until  a  drop  of  the  solution  no 
longer  colours  starch-iodide  paper.2  The  end-point  is  easily  fixed,  since 
the  coloration  of  the  paper  gradually  weakens  beforehand. 

The  number  of  c.c.  of  arsenite  used,  multiplied  by  2,  gives  the  number 
of  litres  of  chlorine  (at  o°  and  760  mm.)  per  kilo  of  substance.  This  repre- 
sents the  chlorometric  degree,  Gay-Lussac  degree  or  French  degree  of  the 
chloride.  To  obtain  the  percentage  of  chlorine  by  weight  (English,  German, 
American  degree],  the  chlorometric  degree  must  be  multiplied  by  0-31698. 

1  4-425  grams  of  arsenious  acid  (puriss.)  and  13  grams  of  crystallised  sodium  car- 
bonate (puriss.)  are  dissolved  in  hot  water  and  the  volume  made  up  to  i  litre  after 
cooling. 

2  3  grams  of  pure  potato  starch  are  mixed  with  250  c.c.  of  cold  water  and  boiled  with 
constant  stirring  ;   2  grams  of  pure  potassium  iodide  and  i  gram  of  crystallised  sodium 
carbonate  are  added  and  the  volume  made  up  to  500  c.c.     Strips  of  filter-paper,  after 
immersion  in  this  liquid,  are  allowed  to  dry  and  kept  in  well  closed  vessels. 


56  BROMINE 

The  same  method  serves  for  determining  the  available  chlorine  in  other 
bleaching  chlorides  such  as  sodium  hypochlorite  (Eau  de  Labarraque)  and 
potassium  hypochlorite  (Eau  de  Javelle],  etc. 

Good  commercial  chloride  of  lime  usually  furnishes  123-127  chlorometric 
degrees,  corresponding  with  39-40%  of  available  chlorine  ;  lower  qualities  give 
as  little  as  95  degrees  (30%  of  chlorine). 


BORAX  AND  NATURAL  BORATES 

The  most  common  sodium  bomte  is  the  prismatic  form,  Na2B407  + 
ioH2O  =  382-26,  with  47-14%  of  water.  There  are  also  Octahedral  borax, 
Na2B407  +  5H2O  =  292-26,  with  30-83%  of  water,  and  Burnt  borax,  Na2B4O7 
=  202-1,  free  from  water.  The  first  two  form  crystals,  prismatic  or  octahe- 
dral, and  the  third  a  fine  powder,  and  all  dissolve  in  water  with  an  alkaline 
reaction. 

Natural  bo  rates  are  :  Boracite  (magnesium  borate  and  magnesium 
chloride,  2Mg3B8O15  +  MgCl2),  Borocalcite  or  Pandermite  (hydrated  calcium 
borate,  Ca2B6Ou  +  4H2O  or  CaB407  +  6H2O)  and  Boronatrocalcite  (cal- 
cium borate  and  sodium  hydroxide). 

Borax  may  contain  the  same  impurities  as  boric  acid  (q.v.).  In  borax 
and  the  natural  borates  the  content  of  boric  acid  must  be  determined  ;  this 
may  be  done  either  by  difference  after  the  water  and  the  impurities  have 
been  determined  or  directly  by  a  volumetric  method. 

Determination  of  the  Boric  Acid. — (a)  IN  BORAX  :  about  30  grams 
of  the  substance  are  dissolved  in  boiled  water  and  the  solution  made  up  to 
I  litre.  50  c.c.  of  the  liquid,  filtered  if  necessary,  are  titrated  in  presence 
of  a  few  drops  of  methyl  orange  with  N/2-acid,  which  combines  with  the 
Na2O  and  liberates  all  the  boric  acid.  50  c.c.  of  glycerine  and  2-3  drops 
of  phenolphthalein  solution  are  then  added  and  the  solution  titrated  with 
N/2-alkali  hydroxide  (absolutely  free  from  carbonates),  as  indicated  under 
Boric  Acid  (5).  I  c.c.  of  N/2-acid  =  0-0155  gram  Na2O  and  i  c.c.  N/2- 
alkali  =  0-0175  gram  B2O3  =  0-0955  gram  Na2B4O7  +  ioH20. 

(b)  IN  NATURAL  BORAXES  :  2  grams  of  the  substance  are  heated,  in  a 
flask  with  a  reflux  condenser,  with  50  c.c.  of  N-acid.  When  cool,  the  con- 
denser is  rinsed  out  and  the  excess  of  acid  neutralised  with  N-alkali  in 
presence  of  methyl  orange.  Glycerine  and  phenolphthalein  are  then  added 
and  the  free  boric  acid  titrated  with  N/2-alkali  as  in  case  (a). 

Crude  borax  may  contain  marked  quantities  of  impurities  (sodium  chloride 
and  sulphate,  calcium  sulphate,  insoluble  matters  and  hygroscopic  water)  ; 
the  refined  product  is  generally  pure  or  almost  so.  The  boronatrocalcite  of 
S.  America  contains  21-44%  B2O3. 

BROMINE 

Br  =  79-92  (80) 

A  dark,  brownish-red,  heavy  liquid  emitting  in  the  air  irritating,  dense 
red  fumes  ;  soluble  in  about  33  parts  of  water,  D  =  2-99  at  15°,  b.pt.  63°. 
It  may  be  contaminated  with  chlorine,  iodine,  sulphuric  acid,  and  organic 


CALCIUM  ACETATE  57 

compounds    (bromoform,    bromocarbonates).     Its    analysis    includes    the 
following  tests  : 

1.  Fixed  Residue. — A  few  grams  of  bromine  are  allowed  to  volatilise 
in  a  porcelain  dish  ;    pure  bromine  leaves  no  weighable  residue. 

2.  Organic   Substances.— A  few  grams  are  dissolved  in  water  and 
excess  of  ammonia  added  ;    in  presence  of  organic  bromine  compounds,  a 
turbid  solution  is  obtained  from  which  oily  drops  may  separate. 

3.  Sulphuric  Acid. — Part  of  the  preceding  ammoniacal  solution  is 
acidified  with  hydrochloric  acid  and  tested  with  barium  chloride. 

4.  Iodine. — Another  part  of  the  ammoniacal  solution  is  evaporated 
to  dryness  and  the  residue  redissolved  in  water  and  treated  with  a  few 
drops  of  ferric  chloride  solution  ;  in  presence  of  iodine,  the  liquid  is  coloured 
yeUow  and  gives  a  violet  colour  to  carbon  disulphide  when  shaken  with  this. 

5.  Chlorine. — Another  part  of  the  ammoniacal  solution  is  evaporated 
to  dryness,  o-i  gram  of  the  residue  being  dissolved  in  10  c.c.  of  water  and 
4  c.c.  of  ammonium  carbonate  solution  (i  part  of  the  carbonate,  i  part  of 
ammonia  of  D  0-96  and  3  parts  of  water)  ;    12  c.c.  of  N/io-silver  nitrate 
are  then  added,  and  the  liquid  heated  for  a  short  time  to  50-60°  and  filtered, 
the  filtrate  being  acidified  with  nitric  acid.     With  pure  bromine,  the  liquid 
is  scarcely  milky,  but  if  chlorine  is  present  a  precipitate  of  silver  chloride 
is  formed. 

For  a  rapid  determination,  which  is  sufficiently  exact,  Kubierschki's 
method  1  may  be  used. 

Commercial  bromine  is  generally  pure  ;  that  of  the  Stassfurt-Leopoldshall 
Mining  Syndicate  is  guaranteed  to  contain  less  than  0-3%  of  chlorine. 

CALCIUM    ACETATE 

Ca(C2H3O2)2  =  158-15 

The  pure  salt  is  put  on  the  market  in  colourless  crystals  extremely 
soluble  in  water,  but  is  of  limited  application  ;  the  crude  salt  (calcium 
•pyrolignite],  in  brownish-grey,  hygroscopic  lumps  or  coarse  powder  with 
a  marked  empyreumatic  odour,  is  an  important  raw  material  for  the  manu- 
facture of  acetic  acid  and  other  acetates.  This  crude  salt  is  always  con- 
taminated with  tarry  substances,  and  also  contains  small  quantities  of 
formate,  propionate  and  other  organic  salts  of  calcium,  calcium  carbonate, 
alumina,  ferric  oxide,  etc.  ;  its  value  depends  on  its  content  of  pure  calcium 
acetate  or  acetic  acid,  so  that  importance  attaches  to  the  quantitative 
determination  of  the  acid. 

Determination  of  the  Acetic  Acid. — Use  is  made  of  a  tubulated 
retort  of  200  c.c.  capacity  placed  on  a  sand-bath,  the  neck  being  turned 
up  a  little  and  connected  with  a  condenser  by  means  of  an  obtuse-angled 
tube.  In  this,  5  grams  of  the  acetate,  50  c.c.  of  water  and  50  c.c.  of  ordinary 
phosphoric  acid  (D  =  1-20)  free  from  nitric  acid  are  heated  and  distilled 
almost  to  dryness,  the  liquid  being  collected  in  a  250  c.c.  n  easuring-flask ; 
after  cooling,  the  retort  is  charged  with  another  50  c.c.  of  water  and  dis- 
tillation almost  to  dryness  repeated.  At  the  end  of  the  distillation,  the 
1  See  Post,  Chem.-techn.  Analyse. 


58  CALCIUM  CARBIDE 

volume  is  made  up  to  the  mark  with  distilled  water  and,  after  mixing, 
50  or  100  c.c.  are  titrated  with  N-alkali  in  presence  of  phenolphthalein. 
I  c.c.  of  N-alkali  =  0-07907  gram  of  anhydrous  calcium  acetate  =  0-06003 
gram  of  acetic  acid. 

It  is  well  to  ascertain  that  the  distillate  does  not  contain  appreciable 
quantities  of  hydrochloric  acid  derived  from  chlorides  in  the  acetate  (silver 
nitrate  should  give  at  most  a  faint  opalescence).  The  small  amounts  of 
propionic  and  butyric  acids,  etc.,  are  practically  negligible. 

*  * 

Crude  calcium  acetate  (pyrolignite)  usually  contains  70-80%  of  true  anhy- 
drous acetate  and  hence  53-60%  of  acetic  acid.  The  pure  calcium  acetate  used 
in  dyeing  is  mostly  prepared  by  the  consumer  himself  by  dissolving  lime  or  cal- 
cium carbonate  in  acetic  acid  ;  it  should  particularly  be  free  from  iron. 

CALCIUM    CARBIDE 

CaC  2  =  64 

Fused  masses  with  crystalline  fracture,  greyish-brown  in  colour  and 
alterable  in  moist  air.  With  water  it  decomposes,  giving  acetylene  and 
calcium  hydroxide.  It  may  contain,  as  impurities,  calcium  sulphide  and 
phosphide,  ammonium  sulphide,  silica,  ferrosilicon  and  silicon  carbide, 
its  value  depending  essentially  on  its  yield  of  acetylene.  The  product 
being  always  non-homogeneous,  special  care  attaches  to  sampling. 

1.  Sampling. — -According   to   the  number   of   casks    (drums)   in   the 
parcel  to  be  analysed,  a  sample  of  at  least  2  kilos  is  taken  from  a  cask  (for 
lots  up  to  20  drums)  or  from  5%  or  10%  of  the  casks  (for  lots  of  more  than 
20  drums).     Before  being  opened  the  cask  is  inverted  twice  to  distribute 
the  small  pieces  and  dust  as  uniformly  as  possible  throughout  the  coarse. 
The  sample  is  placed  immediately  in  glass  vessels  with  ground  stoppers  or 
in  metal  vessels  with  soldered  lids.1 

2.  Various  Impurities. — As  a  rule  the  carbide  itself  is  not  investi- 
gated, it  being  sufficient  to  determine  the  yield  of  acetylene  and  to  test 
the  purity  of  the  gas  (see  below).     Where  necessary,  however,  the  carbide 
may  be  treated  with  a  sugar  solution  in  which  the  lime  remains  dissolved, 
whereas  the  impurities  remain  undissolved  and  may  be  recognised  by  the 
ordinary  analytical  methods.     As  a  rule  these  impurities  represent  3-6% 
of  the  carbide. 

3.  Yield  of  Acetylene. — This  is  determined  by  treating  a  known  weight 
of  the  carbide  with  water  (or,  better,  brine)  and  measuring  the  volume  of 
gas  evolved.     Various  forms  of  gasometer  or  apparatus  may  be  used  to 
collect  and  measure  the  gas.2 

The  determination  may  be  made  in  one  of  two  methods  :  Total  gasifica- 
tion, which  consists  in  decomposing  with  water  (in  one  or  more  lots)  the 
whole  of  the  sample  as  it  is  taken,  and  Partial  gasification,  which  consists 

1  See  also  Acetylene,  by  V.  B.  Lewes   (New  York,  1900),   Post,   Chem.-techn.  Analyse. 

2  See  works  cited  in  preceding  note,  and  also  articles  by  Formenti  in  La  chimica 
industrial,  1902,  Vol.  VI,  p.  182  ;  Recchiin  Gazz.  chim.  ital.,  1903, 1,  p.  153  ;  Magnanini 
and  Vannini,  ibid.,  1900,  I,  p.  401. 


CALCIUM  CITRATE  59 

in  powdering  the  sample  rapidly  and  then  decomposing  two  or  more  aliquot 
parts  of  the  powder. 

4.  Purity  of  the  Acetylene. — The  acetylene  may  contain  various 
impurities,  such  as  hydrogen  phosphide  and  sulphide,  ammonia,  hydrogen, 
nitrogen,  oxygen  and  carbonic  oxide.  Of  these  the  most  important  to 
detect  and  estimate  is  hydrogen  phosphide.  Lunge  and  Cedercreutz's 
method  may  be  used  for  this  purpose  :  50  grams  of  the  carbide  are  placed 
in  a  flask  of  about  £  litre  capacity  closed  by  a  stopper  with  two  holes,  through 
one  of  which  passes  a  tapped  funnel  and  through  the  other  a  right-angled  tube 
connected  with  a  tube  with  10  bulbs  into  which  are  poured  75  c.c.  of  2-3% 
sodium  hypochlorite  solution.  From  the  funnel  water  is  dropped  slowly 
on  to  the  carbide,  which  is  occasionally  shaken.  When  the  evolution  of 
gas  ceases,  the  flask  is  nearly  filled  with  water  and  gentle  suction  applied 
to  the  bulb-tube,  so  that  all  the  gas  traverses  the  hypochlorite.  The  con- 
tents of  the  bulb-tube  are  then  introduced  into  a  beaker  and  the  phosphoric 
acid  (formed  by  the  action  of  the  hypochlorite  on  the  hydrogen  phosphide) 
precipitated  with  magnesia  mixture  (see  Fertilisers).  I  gram  of  magnesium 
pyro phosphate  =  0-81982  gram  of  calcium  phosphide  (Ca3P2)  =  200-86 
c.c.  of  hydrogen  phosphide  (PH3). 

*** 

Commercial  calcium  carbide  in  lumps  or  pieces  should  not  contain  more 
than  5%  of  fine  dust  passing  through  a  sieve  of  i  mm.  mesh,  and  the  impurities 
should  not  exceed  3-6%.  Good  carbide  usually  gives  about  300  litres  (at  15°  and 
760  mm.)  of  acetylene  per  kilo,  whilst  the  chemically  pure  product  should  give 
348-8  litres.  A  commercial  carbide  should  not  give  less  than  270  litres  per  kilo, 
with  an  allowance  of  2%  on  the  analytical  results.  The  impurities  in  the  gas 
should  not  exceed  i%.  Of  these  hydrogen  sulphide  or  ammonia  is  found  rarely 
and  only  in  traces,  but  hydrogen  phosphide  occurs  in  relatively  large  propor- 
tions ;  Lunge  and  Cedercreutz  have  found  from  0-031  to  0-061%  by  volume, 
which  would  correspond  with  about  0-038-0-075  gram  of  calcium  phosphide 
per  kilo  of  carbide  (with  a  yield  of  300  litres  of  gas). 


CALCIUM    CITRATE 

Ca3(C6H607)2  +  4H20  =  570 

Crude  calcium  citrate,  prepared  largely  in  Sicily,  serves  as  raw  material 
for  the  preparation  of  citric  acid.  It  forms  yellowish-grey  clots  or  powder 
with  a  slight  biscuity  odour  and  dissolves  slightly  in  cold  water  with  an 
alkaline  reaction  and  still  less  in  hot  water.  It  consists  mostly  of  calcium 
citrate,  mixed  with  calcium  carbonate  and  oxide,  with  small  proportions 
of  other  salts  and  organic  compounds  of  calcium,  ferric  oxide,  alumina, 
silica,  etc.  ;  in  some  cases  it  contains  magnesia  and  strontia. 

The  commercial  value  of  calcium  citrate  depends  on  the  quantity  of 
crystallised  citric  acid  corresponding  with  the  pure  calcium  citrate  con- 
tained in  the  product.  The  quantitative  estimation  of  the  citric  acid 
hence  occupies  first  place  in  the  analysis ;  then  come  determinations  of 
the  alkalinity,  hygroscopic  moisture  and  ash,  and  a  partial  qualitative 
analysis  to  detect  any  such  adulteration  as  sulphate,  oxalate,  phosphate, 
tartrate  of  calcium,  etc. 


60  CALCIUM  CITRATE 

Preparation  of  the  Sample. — Prior  to  the  analysis,  the  sample  must 
be  thoroughly  mixed  by  pounding  in  a  glass  mortar  and  passing  it  several 
times  through  a  fine  sieve.  The  sample  is  then  stored  in  tight  vessels. 

1.  Alkalinity. — About  5  grams  are  carefully  boiled  for  some  minutes 
in  a  100  c.c.  flask  with  25-30  c.c.  of  N/2-hydro chloric  acid  ;    on  cooling, 
the  excess  of  acid  is  titrated  with  N/2-alkali  in  presence  of  phenolphthalein. 
The  alkalinity  is  expressed  as  calcium  carbonate,  so  that  the  number  of 
c.c.  of  acid  neutralised,  multiplied  by  0-025,  gives  the  alkalinity  referred 
to  100  grams  of  the  citrate. 

2.  Loss  of   Weight  at  100°. — 2-3  grams  are  dried  in  a  steam-oven 
for  about  5  hours  in  a  weighing  bottle  5  cm.  wide  and  3  cm.  high,  weighed 
and  again  heated  to  constant  weight.     The  loss  of  weight  is  referred  to  100 
grams  of  citrate,  which,  when  pure,  loses  4-73%  of  water  of  crystallisation. 

3.  Hygroscopic  Water. — From  the  loss  in  weight  at   100°  and   the 
percentage  of  citric  acid  or,  better,    calcium  citrate  (see  6,  below)  in  the 
sample  the  hygroscopic  moisture  is  calculated. 

Example  :  A  sample  of  citrate  contains  62-40%  of  citric  acid  or  84-72%  of 
pure  calcium  citrate,  and  loses  in  the  steam-oven  5-o8%  of  its  weight.  Since 
100  grams  of  pure  citrate  lose  4-73  grams,  the  water  of  crystallisation  lost  by  the 
calcium  citrate  in  the  sample  will  be  given  by 

zoo  :  4-73  :  :  84-72  :  x 
x  =  4-00. 

The  hygroscopic  moisture  is,  therefore,  5-08-4-00  =  1-08%. 

With  commercial  citrates  this  procedure  gives  only  approximate  results, 
since  the  other  substances  present  may  influence  the  loss  of  weight  in  one  direc- 
tion or  the  other. 

4.  Ash. — About  10  grams  in  a  platinum  dish  are  heated  first  gently 
over  a  gas  flame  and  then  at  a  red  heat  in  a  muffle  for  an  hour. 

5.  Impurities. — (a)  PHOSPHATES.     The    citrate    is    sometimes  adul- 
terated with  calcium  phosphate.     Part  of  the  ash  is  heated  with  nitric 
acid  and  the  solution  filtered  and  tested  for  phosphoric  acid  by  means  of 
ammonium  molybdate. 

(&)  MAGNESIUM  AND  STRONTIUM.  For  these  the  ash  is  tested  by  the 
ordinary  methods. 

(c)  OXALATES.     About  8  grams  are  dissolved  in  hot,  dilute  hydrochloric 
acid,  filtered  and  the  filtrate  made  up  to  200  c.c.  (solution  a). 

50  c.c.  of  this  solution  are  diluted  with  distilled  water,  rendered  alkaline 
with  caustic  soda  and  then  acidified  with  concentrated  acetic  acid  :  no 
turbidity  should  appear. 

(d)  SULPHATES.     To  50  c.c.  of  solution  a  barium  chloride  in  slight  excess 
is  added. 

(e)  TARTRATES.     The  remaining  100   c.c.   of  solution  a  are  rendered 
alkaline  with  potassium  carbonate  and  evaporated  to  dryness.     The  residue 
is  taken  up  in  a  little  boiling  water  and  filtered,  the  filtrate  being  acidified 
distinctly  with  acetic  acid  and  10  vols.  of  95%  alcohol  added.     The  crystal- 
line precipitate  obtained  is  filtered  off,  washed  two  or  three  times  with 
alcohol  and  dried  in  a  steam-oven.     A  very  small  quantity  of  resorcinol 
and  a  few  drops  of  concentrated  sulphuric  acid  are  gently  heated  in  a  por- 
celain dish  until  white  fumes  are  emitted  and  a  few  crystals  of  the  above 


CALCIUM  CITRATE  61 

precipitate  added  and  gentle  heat  again  applied.  A  distinct  wine-red 
coloration  indicates  the  presence  of  tartaric  acid. 

6.  Determination  of  the  Citric  Acid. — 10  grams  of  the  citrate  are 
boiled  gently  in  a  graduated  250  c.c.  flask  with  22  c.c.  of  hydrochloric  acid 
of  D  i'io  and  about  50  c.c.  of  distilled  water  to  expel  the  carbon  dioxide 
completely.  When  cold,  the  liquid  is  made  up  to  the  mark,  shaken  and 
filtered  through  a  dry  paper.  50  c.c.  of  the  filtrate  (=  2  grams  of  the 
citrate)  are  neutralised  exactly  with  approximately  2N-caustic  soda  free 
from  carbonate,  using  phenolphthalein  as  indicator.  After  addition  of 
2  c.c.  of  roughly  40%  calcium  chloride  solution,  the  liquid  is  made  faintly 
acid  with  a  few  drops  (4-6)  of  N/2-hydrochloric  acid. 

This  liquid,  in  a  beaker  of  resistant  glass,  is  kept  for  half  an  hour  im- 
mersed in  a  bath  of  boiling  brine  and  then  filtered  hot  through  a  rapid 
filter,  on  to  which  the  calcium  citrate  precipitate  is  washed  as  completely 
as  possible  with  hot  water  ;  the  precipitate  is  washed  with  boiling  water, 
not  more  than  150  c.c.  being  used  altogether.  The  precipitate  (I)  is  then 
dried  in  a  steam-oven,  while  the  filtrate  is  neutralised  with  a  few  drops  of 
dilute  ammonia  (i  :  6)  and  concentrated  to  30-40  c.c.  in  the  beaker  pre- 
viously used  for  the  precipitation.  The  liquid  is  then  placed  in  a  smaller 
beaker  (50  c.c.),  another  drop  of  ammonia  being  added  and  the  concentra- 
tion continued  to  15  c.c.  The  precipitate  is  then  collected  on  a  small  filter 
and  rapidly  washed  with  small  quantities  of  boiling  water. 

This  precipitate  (II)  is  dried  and  the  filtrate,  treated  as  before  with  a 
little  dilute  ammonia,  concentrated  by  boiling  to  10  c.c.  The  precipitate 
(III)  is  collected  on  a  small  filter,  washed  with  very  small  amounts  of  boiling 
water  and  dried  in  the  steam-oven. 

The  three  dry  precipitates  are  incinerated  with  the  filter-papers  in  a 
platinum  dish  and  the  latter  kept  in  a  muffle  at  redness  for  30  minutes. 
The  ash  is  then  treated  with  50  c.c.  of  N/2-hydrochloric  acid,  which  is  added 
to  the  dish  in,  small  portions,  and  then  transferred  to  a  flask.  The  liquid 
is  boiled  carefully  to  dissolve  the  ash  completely,  then  cooled  and  the  excess 
of  acid  titrated  with  N/4-potassium  hydroxide  in  presence  of  phenolphtha- 
lein. The  quantity  of  citric  acid  is  then  calculated  ;  i  c.c.  of  N/4-alkali  = 
0-0175  gram  of  crystallised  citric  acid  or  0-875%  on  the  sample. 

This  method  has  been  officially  adopted  in  Italy  for  the  analysis  of  crude 
citrate  'and  concentrated  lemon  juice. 

^Tiere  marked  quantities  of  tartrate  have  been  found,  it  is  advisable  not  to 
concentrate  the  solutions  much  for  collecting  precipitates  II  and  III — instead 
of  15  and  10  c.c.  only  to  20  and  15  c.c.  respectively. 

In  case  sulphates  are  present,  the  ash  from  the  precipitates  should  be  treated 
with  10  c.c.  of  3%  hydrogen  peroxide  solution,  which  is  then  slowly  evaporated 
on  a  water-bath,  the  treatment  with  50  c.c.  of  N/2-hydrochloric  acid  being  after- 
wards carried  out  as  described  above. 

* 
*    * 

Crude  calcium  citrate  contains  64-70%  of  crystallised  citric  acid  (+  iH2O) 
in  combination  with  lime  ;  usually  the  percentage  varies  between  64  and  66, 
but  impure  samples  containing  59-63%  are  not  rare. 

The  alkalinity  of  the  crude  citrate,  deduced  from  the  free  lime  and  calcu- 
lated as  calcium  carbonate,  should  not  exceed  2%,  otherwise  the  price  is  subject 
to  reduction. 


62  CARBON  TETRACHLORIDE 

The  ash  of  the  crude  citrate  is  usually  grey  owing  to  the  presence  of  ferric 
oxide  and  contains  alumina,  silica  and  alkalies  ;  magnesium  and  aluminium, 
when  present,  should  be  in  very  small  proportions.  These  two  metals  come  from 
impure  lime  used  in  the  manufacture  of  the  citrate  and  lower  the  yield  of  the 
latter  appreciably.  Further,  sulphates,  phosphates  and  oxalates  should  occur 
only  in  minimal  proportions. 

In  the  steam-t)ven,  crude  citrates  lose  4-6%  of  their  weight.  The  pure 
citrate  loses  4-73%  at  100°. 


CARBON    BISULPHIDE 

CS2  =  76 

A  colourless  or  yellowish  liquid,  of  ethereal  odour  if  highly  pure  but 
usually  of  repulsive  smell  owing  to  the  presence  of  traces  of  organic  sulphur 
compounds.  It  is  very  readily  inflammable,  D  —  1-272,  b.pt.  46-47°, 
insoluble  in  water.  The  commonest  impurity  is  sulphur,  and  it  may  contain 
also  hydrogen  sulphide,  sulphurous  and  sulphuric  acids.  The  principal 
tests  are  as  follows. 

1.  Sulphur. — 5  c.c.,  allowed  to  evaporate  spontaneously  in  a  tared 
glass  dish,  should  leave  no  weighable  residue  ;    or  about  2  c.c.  is  shaken 
with  a  drop  of  dry,  clean  mercury,  and  note  made  if  this  becomes  covered 
with  a  brown,  powdery  layer. 

2.  Hydrogen  Sulphide. — The  liquid  is  shaken  with  a  little  lead  car- 
bonate, which  blackens  in  presence  of  hydrogen  sulphide. 

3.  Sulphurous  and  Sulphuric  Acids. — The  sulphide  is  shaken  with 
water  coloured  with  a  drop  of  neutral  litmus  solution  and  any  decolorisa- 
tion  or  reddening  of  the  water  noted. 

CARBON    TETRACHLORIDE 

CC14  =  153-84 

Colourless  liquid  of  ethereal  odour,  D  =  1-6,  b.pt.  76-77°,  insoluble  in 
water,  miscible  in  all  proportions  with  alcohol  or  ether.  It  may  be  con- 
taminated with  chlorine,  hydrochloric  acid,  aldehydes,  various  organic 
impurities  and  carbon  bisulphide.  The  tests  to  be  made  are  as  follows  : 

1.  Volatility. — 25  c.c.,  evaporated  on  a  steam-bath,  should  leave  no 
appreciable  residue. 

2.  Chlorine  and  Hydrochloric  Acid. — See  Chloroform. 

3.  Aldehydes. — 10  c.c.  are  shaken  with  10  c.c.  of  potassium  hydroxide 
solution  (i  :  3)  and  heated  for  i  minute  :    the  aqueous  liquid  should  not 
colour. 

4.  Organic  Impurities. — 20  c.c.  are  shaken  with  15  c.c.  of  pure  cone, 
sulphuric  acid,  which  should  not  colour  within  an  hour. 

5.  Carbon  Bisulphide. — 10  c.c.  are  mixed  with  10  c.c.  of  alcoholic 
potassium  hydroxide  (i  gram  in  10  c.c.  of  absolute  alcohol)  ;    after  an 
hour,  the  liquid  is  faintly  acidified  with  acetic  acid  and  1-2  drops  of  dilute 
copper  sulphate  solution  added  ;  no  browning  or  yellow  precipitate  (potas- 
sium xanthate)  should  be  produced  within  two  hours. 


COPPER  SULPHATE  63 

CHLORIDE    OF    LIME 

See  Bleaching  Powder 

CHLOROFORM 

CHC13  =  119-38 

Colourless  heavy  liquid  of  peculiar  odour,  D  =  1-490-1 -493,  b.pt.  61- 
62°,  very  slightly  soluble  in  water,  miscible  with  alcohol.  The  impurities 
to  be  looked  for  are  especially  chlorine,  hydrochloric  acid,  chloro-compounds 
(of  ethylidene  and  amyl)  and  aldehydes,  the  tests  being  carried  out  as 
follows  : 

1.  Volatility. — 20-30  c.c.,   evaporated  spontaneously  or  at  a  gentle 
heat,  should  leave  no  appreciable  residue  of  unpleasant,  irritating  odour 
(phosgene,  amyl  or  valeric  corn-pounds}. 

2.  Reaction,  Hydrochloric  Acid. — To  5  c.c.  are  added  i  drop  of  a 
saturated  solution  of  Congo  red  in  absolute  alcohol :   if  the  chloroform  has 
undergone  change,  a  blue  coloration  appears. 

5  c.c.  are  shaken  with  2-5  c.c.  of  water,  which  should  not  become  acid 
or  give  a  turbidity  with  silver  nitrate  (hydrochloric  acid). 

3.  Other  Tests. — 5  c.c.,  shaken  with  potassium  iodide  solution  or 
with  iodide-starch  paste,  should  give  no  red  or  blue  coloration  (chlorine). 

20  c.c.,  shaken  with  12  c.c.  of  pure  cone,  sulphuric  acid,  should  give  no 
brownish-yellow  coloration,  even  after  24  hours  (chlorinated  ethylidene  or 
amyl  compounds). 

A  fragment  of  caustic  potash,  added  to  5  c.c.  of  the  sample,  should 
remain  white  and  the  liquid  should  not  turn  yellow  in  12  hours. 

Pure  chloroform  for  medical  purposes  should  answer  all  the  above  tests. 
It  is  permissible  to  add  0-5-1%  of  alcohol  as  a  preservative. 

COPPER  SULPHATE 

CuS04  +  5H20  =  249-57 

Blue  crystals  which  effloresce  somewhat  in  the  air,  soluble  in  3-5  parts 
of  cold  water.  It  is  sold  fairly  pure,  only  containing,  as  a  rule,  small  quan- 
tities of  ferrous  sulphate  and  rarely  zinc,  magnesium  and  calcium  sulphates 
or  free  sulphuric  acid.  Its  value  depends  on  the  proportion  of  pure  crys- 
tallised copper  sulphate  and  its  analysis  includes  mainly  determinations 
of  the  copper  and  water  (3  and  4).  In  some  cases  determinations  of  the 
iron  and  free  sulphuric  acid  may  be  required. 

1 .  Iron. — 4  grams  are  dissolved  in  20  c.c.  of  water,  an  excess  of  ammonia 
added,  the  liquid  filtered  and  the  filter  washed  until  it  is  no  longer  blue ; 
in  presence  of  iron,  a  brownish  deposit  or  spot  remains  on  the  filter. 

2.  Zinc,   Magnesium,   Calcium  and  other   Metals. — 2  grams  are 
dissolved  in  40  c.c.  of  water,  the  solution  being  acidified  with  hydrochloric 
acid  and  the  copper  precipitated  with  hydrogen  sulphide  ;    the  filtered 
liquid,  evaporated  and  ignited,  should  leave  no  appreciable  residue.     If 


64  COPPER  SULPHATE 

this  is  not  the  case,  the  extraneous  substances  are  examined  in  the  ordinary 
way. 

3.  Determination  of  the  Copper. — This  may  be  carried  out  electro- 
lytically  or  volumetrically. 

(a)  ELECTROLYTIC    DETERMINATION.    4-5    grams    of   the    sample,    as 
homogeneous  as  possible,  are  dissolved  in  about  200  c.c.  of  water  with 
gentle  heating  ;   5—6  c.c.  of  cone,  nitric  acid  and  20  c.c.  of  dilute  sulphuric 
acid  (10%  by  volume)  are  added  and  the  solution  electrolysed  (see  article 
on  Copper  in  chapter  on  Metals).     The  conditions  of  working  are  as  follows  : 
Winkler    electrodes  ;     ND100  =  0-3-0-4    ampere  ;     voltage,    2-2-2    volts  ; 
temperature,  ordinary ;    duration,  16-18  hours. 

The  weight  of  copper  found,  multiplied  by  3-9283,  gives  the  sulphate 
of  copper,  CuSO4  +  5H2O. 

(b)  VOLUMETRIC  DETERMINATION  (Zecchini's  method  1).    For  this  method 
the  following  reagents  are  required  : 

(#)  Solution  containing  19-878  grams  of  crystallised  sodium  thiosulphate 
per  litre  and  another,  8  grams  of  ammonium  thiocyanate  per  litre. 

(b)  Iodine  solution  containing  5-089  grams  of  iodine  and  20-25  grams 
of  potassium  iodide  per  litre. 

(c)  Pure  copper  sulphate  solution  containing  20  grams  of  the  crystals 
per  litre. 

Solutions  (a)  and  (c)  are  of  corresponding  strength  and  2  vols.  of  (b) 
correspond  with  I  vol.  of  (a). 

In  a  porcelain  dish  are  placed  60  c.c.  of  solution  (a)  and  a  little  starch 
paste  z ;  solution  (&)  is  then  run  in  from  a  burette  until  a  persistent  blue 
coloration  appears.  To  another  60  c.c.  of  (a)  are  added,  with  stirring, 
50  c.c.  of  solution  (c)  (=  i  gram  of  CuSO4,  5H2O)  and  10  c.c.  of  starch 
paste,  this  being  titrated  with  iodine  (b)  as  before. 

The  difference  (n)  between  the  volumes  of  (b)  used  in  the  two  cases 
corresponds  with  i  gram  of  CuSO4,  5H2O,  and  with  pure  materials  under 
the  above  conditions,  this  difference  is  very  nearly  100  c.c.,  as  it  should  be. 

The  operation  is  then  repeated  with  a  solution  (20  grams  per  litre)  of 
the  sulphate  to  be  tested,  50  c.c.  being  taken  and  the  volume  of  the  iodine 
solution  necessary  measured.  If  n1  is  the  difference  in  the  volume  of  (b) 
used  in  this  case,  the  percentage  of  pure  crystallised  copper  sulphate  is 
(100  X  n^/n. 

4.  Water. — 5  grams  of  the  powdered  sulphate  are  weighed  in  a  platinum 
crucible,  which  is  supported  on  a  porcelain  triangle  inside  a  larger  iron 
crucible  ;   the  latter  is  heated  for  15  minutes  with  a  large  Teclu  flame,  the 
platinum  crucible  being  then  cooled  in  a  desiccator  and  weighed. 

5.  Iron. — 5-10  grams,  dissolved  in  100-150  c.c.  of  water,  are  heated 
for  15  minutes  on  a  steam-bath  with  5-10  c.c.  of  nitric  acid,  the  iron  being 
then  precipitated  with  a  slight  excess  of  ammonia  and  weighed  as  Fe2O3 : 
Fe203  X  3-475  =  FeSO4  +  7H2O. 

6.  Free   Sulphuric  Acid. — 10  grams  are  dissolved  to  500  c.c.,  the 

1  Stazioni  agrarie  italiane,  Vol.  XXXII,  p.  120. 

*  3  grams  of  starch  arc  mixed  to  a  paste  with  a  little  water  and  poured  into  200  c.c. 
of  boiling  water,  the  solution  being  boiled  for  a  minute  and  allowed  to  cool. 


FERRIC  CHLORIDE  65 

acidity  being  determined  on  an  aliquot  part    by  N/io-alkali,  Congo-red 

paper  being  used  as  indicator,     i  c.c.  N/io-alkali  =  0-0049  gram  H2SO4. 

Commercial  copper  sulphate  usually  contains  98-99-5%  of  CuSO4  +  5H2O. 


ETHER 

C4H100  =  74 

Colourless,  light,  highly  volatile,  neutral  liquid,  of  peculiar  odour, 
D  ==  0-720-0-722,  b.pt.  35°,  slightly  soluble  in  water  (10-12%)  and  miscible 
with  alcohol.  Commercial  ether  almost  always  contains  more  or  less 
marked  quantities  of  water,  alcohol  and  free  acids  ;  old  aqueous  ether  may 
contain  hydrogen  peroxide  or  other  peroxidised  compounds,  which  may 
cause  explosions  when  the  ether  evaporates.  The  tests  to  be  made,  besides 
determinations  of  the  density  and  boiling  point,  are  as  follows  : 

1.  Water. — When    shaken    with    aqueous    ether,    anhydrous    copper 
sulphate  is  coloured  blue,  whereas  if  the  ether  is  anhydrous  it  remains 
white.     A  piece  of  freshly  cut  sodium,  immersed  in  perfectly  anhydrous 
ether,  retains  its  lustre  for  some  hours ;    if  the  ether  is  wet,  the  sodium 
becomes  covered  immediately  with  an  opaque  layer,  while  copious  evolution 
of  hydrogen  occurs. 

2.  Alcohol. — 10  c.c.,  shaken  with  as  much  water  (in  a  closed  cylinder), 
should  not  diminish  in  volume  by  more  than  one-tenth  ;  the  water  separated 
should  not  give  the  iodoform  reaction  with  iodine  and  caustic  soda. 

3.  Acidity. — To  20  c.c.  are  added  10  c.c.  of  water  and  a  few  drops  of 
phenolphthalein  and,  after  shaking,  the  volume  of  standard  alkali  necessary 
to  produce  a  red  coloration  determined.     With  a  good  sample  this  should 
not  exceed  o*i-o-2  c.c.  of  N/ioo-alkali. 

4.  Hydrogen  or  other  Peroxide. — 10  c.c.   are  shaken  in  a  closed 
cylinder  with  I  c.c.  of  i  :  10  potassium  iodide  solution  :   with  pure  ether, 
no  coloration  should  occur,  even  after  an  hour's  stand  in  the  dark. 

5.  Aldehydes,   Vinyl   Products. — 5   c.c.    should  give   no   coloration 
within  5  minutes  with  i  c.c.  of  water  and  5  drops  of  Nessler  reagent. 

6.  Sulphur  Compounds. — 10  c.c.  are  shaken  with  a  few  drops  of 
weh1  cleaned  mercury,  which  becomes  brown  or  black  in  presence  of  sulphur 
compounds. 

FERRIC    CHLORIDE 

FeCl3  +  6H2O  =  270-22 

Orange-yellow,  deliquescent,  crystalline  masses,  which  may  contain 
oxychloride  (insoluble),  free  chlorine  and  hydrochloric  acid,  ferrous  chloride, 
arsenic,  nitrates  and  extraneous  metals. 

1 .  Solubility. — i  part  of  the  salt  and  i  part  of  water  should,  in  absence 
of  oxychloride,  give  a  clear  solution  which  remains  clear  after  addition  of 
5  vols.  of  alcohol. 

2.  Free  Chlorine  and  Hydrochloric  Acid. — In  the  vessel  containing 
the  salt  are  suspended  a  moistened  starch-iodide  paper  and  a  glass  rod  wet 

A.C.  5 


66  FERROUS   SULPHATE 

with  ammonia  :  in  presence  of  chlorine,  the  paper  turns  blue  and  in  presence 
of  hydrochloric  acid  white  fumes  form  round  the  rod. 

3.  Ferrous  Chloride. — The  i  :  100  solution  is  tested  with  a  few  drops 
of  freshly  prepared  dilute  potassium  ferricyanide  solution  :    in  presence 
of  ferrous  salts  a  blue  coloration  is  formed. 

4.  Arsenic. — -To  i  c.c.  of  the  i  :  i  solution,  5  c.c.  of  Bettendorf's  re- 
agent are  added  :    no  brown  coloration  should  be  formed  within  an  hour. 

5.  Nitrates  and  Extraneous  Metals. — i  gram,  dissolved  in  20  c.c. 
of  water,  is  treated  with  excess  of  ammonia  and  filtered.     2  c.c.  of  the 
filtrate  are  boiled  until  the  ammonia  is  completely  expelled  and  is  then 
mixed  with  cone,  sulphuric  acid,  ferrous  sulphate  solution  being  poured 
carefully  on  to  the  surface  of  the  liquid  :    any  brown  ring  at  the  zone  of 
contact  of  the  two  layers  is  observed  (nitric  acid}. 

The  remainder  of  the  nitrate  is  evaporated  to  dryness  and  calcined  to 
ascertain  if  appreciable  residue  remains  (extraneous  metals}. 

FERROUS  ACETATE 

Industrial  use  is  made  of  crude  ferrous  acetate  (pyrolignite  of  iron} 
solution,  which  is  a  greenish-black  liquid  of  marked  empyreumatic  odour. 
This  solution  is  usually  of  12-15°  Baume,  but  stronger  ones  of  20-30°  Baume 
are  also  prepared,  these  containing  more  tarry  matters  which  are  precipitated 
on  dilution. 

1.  Grade. — Determined  with  an  ordinary  Baume  hydrometer. 
'  2.  Behaviour  on  Dilution. — i  vol.  is  diluted  with  250  vols.  of  water 
and  the  colour  of  the  liquid  and  any  precipitation  of  tarry  substances  noted. 

3.  Ferric  Salts. — The  sample  is  diluted  i  :  10,  acidified  with  hydro- 
chloric acid  and  tested  with  potassium  ferrocyanide. 

4.  Sulphates,  Chlorides. — The  i  :  10  solution  of  the  sample  is  acidified 
with  nitric  acid  and  tested  with  barium  chloride  and  with  silver  nitrate. 
An  appreciable  proportion  of  sulphate  is  determined  as  barium  sulphate, 
while  hydrochloric  acid  may  be  estimated  as  silver  salt. 

5.  Determination  of  the  Acetic  Acid. — This  is  done  as  in  calcium 
acetate  (q.v.}. 

6.  Determination  of  the  Iron. — 1-2  grams  are  evaporated  to  dryness 
and  the  residue  cautiously  ignited  and  dissolved  in  hydrochloric  acid,  the 
iron  being  determined  in  the  solution  by  precipitation  with  ammonia. 

Pyrolignite  of  iron  solution  or  mordant  for  black  (not  to  be  confused  with  the 
basic  sulphate),  when  diluted  with  water  (test  2),  should  give  a  fine  blue  colora- 
tion, which  slowly  changes  to  greenish  and  becomes  opaque ;  it  should  not  con- 
tain any  large  proportions  of  ferric  salts  or  sulphates. 

FERROUS    SULPHATE 

FeSO4  +  7H2O  =  278 

Forms  large  or  small,  pale  green  crystals  or  crystalline  powder  ;  in  the 
air  it  effloresces  somewhat,  and  it  dissolves  in  1-5  parts  of  water  and  is 
insoluble  in  alcohol.  It  often  exhibits  yellowish  spots  of  ferric  oxide  or 


FORMALDEHYDE  67 

sulphate.     As   impurities   it   may   contain   especially   copper,    zinc,    man- 
ganese, magnesium,  arsenic,  ferric  salts  and  free  sulphuric  acid. 

1.  Copper,  Zinc. — 3  grams  are  dissolved  in  water,  boiled  with  nitric 
acid,  and  precipitated  with  excess  of  ammonia  ;  after  filtration,  the  nitrate 
is  tested  for  copper  and  zinc  by  the  ordinary  methods. 

2.  Ferric  Salts. — The  sample  is  dissolved  in  recently  boiled  water, 
acidified  with  a  little  hydrochloric  acid  and  tested  with  ammonium  thio- 
cyanate. 

3.  Free  Sulphuric  Acid. — The  aqueous  solution,  prepared  with  boiled 
water,  should  not  redden  blue  litmus  paper. 

4.  Other  Impurities. — 3  grams  are  dissolved  in  water  and  oxidised 
by  boiling  with  nitric  acid  ;    after  precipitation  with  ammonia  and  nitra- 
tion, the  lime,  magnesia,  arsenic  and  any  other  impurities  are  sought  in  the 
filtrate. 

FORMALDEHYDE 

CH2O  =  30 

This  is  sold  in  aqueous  solution  under  the  name  Formal  or  Formalin 
and  is  a  colourless  liquid  with  a  peculiar,  irritating  odour,  D  =  about  1-08  ; 
it  contains  35-40  grams  of  formaldehyde  per  100  c.c.  The  commercial 
product  may  be  contaminated  with  formic  and  acetic  acids,  methyl  alcohol, 
acetone,  chlorides,  sulphates,  copper  and  calcium ;  its  value  depends 
essentially  on  the  content  of  formaldehyde. 

1.  Acidity. — Tested  with  litmus  paper  ;   an  acidity  corresponding  with 
a  drop  of  N-alkali  per  i  c.c.  of  the  sample  is  allowable. 

2.  Sulphuric  Acid,  Hydrochloric  Acid,  Metals.— These  are  detected 
in  the  i  :  5  solution  in  the  usual  way. 

3.  Methyl  Alcohol. — 50  c.c.  are  treated  with  100  c.c.  of  10%  ammonia, 
with  which  the  formaldehyde  combines,  forming  hexamethylenetetramine  ; 
after  a  rest  of  6  hours  in  a  closed  vessel,  the  greater  part  of  the  liquid  is 
distilled  off.     The  distillate  is  acidified  with  a  slight  excess  of  dilute  sulphuric 
acid  and  redistilled,  the  temperatures  at  which  the  first  fractions  distil 
being  observed  :    in  presence  of  methyl  alcohol,  these  will  come  over  at 
about  66°  and  may  be  tested  for  methyl  alcohol  (see  Spirits  :   Detection  of 
Denaturants). 

By  collecting  50  c.c.  of  distillate  (after  acidification)  and  determining 
its  specific  gravity,  the  quantity  of  methyl  alcohol  present  may  be  found 
approximately  from  the  table  on  p.  40. 

4.  Acetone. — A  few  c.c.  are  treated  with  sodium  hydroxide  and  iodine 
solution  :    in  presence  of  acetone,  iodoform  is  formed  immediately  in  the 
cold. 

5.  Determination    of   the    Formaldehyde    (lodometric    method   of 
Fresenius  and  Grunhut). — 25  c.c.  are  diluted  with  water  to  500  c.c.  and 
5  c.c.  of  the  solution  (=  0-25  c.c.  of  substance)  introduced  into  a  bottle 
of  about  200  c.c.  capacity  fitted  with  a  ground  stopper  ;   30  c.c.  of  N-sodium 
hydroxide  are  then  added  rapidly  from  a  graduated  cylinder  and,  from  a 
burette  and  with  shaking,  50  c.c.  of  N/5-iodine  solution  (the  liquid  should 


68  HYDROGEN   PEROXIDE 

remain  yellow).  The  vessel  is  then  closed  and  shaken  vigorously  for  half 
a  minute,  after  which  40  c.c.  of  N-sulphuric  acid  are  added  from  a  graduated 
cylinder.  The  vessel  is  again  closed  and  left  for  a  few  minutes,  the  excess 
of  iodine  being  then  titrated  with  N/io-sodium  thiosulphate  solution. 
2  c.c.  of  N/io-thiosulphate  =  i  c.c.  N/5-iodine  =  0-003  gram  CH2O.  The 
number  of  c.c.  of  N/5-iodine  consumed  x  1-2  =  grams  of  CH2O  per  100  c.c. 

This  method  is  not  applicable  in  presence  of  acetone,  at  any  rate  in  appre- 
ciable quantity;  as  a  rule,  however,  the  proportion  of  acetone  is  small. 

* 
*   * 

Commercial  formaldehyde  should  contain  not  less  than  35  grams  of  CH2O 
per  100  c.c.  Methyl  alcohol  is  often  added  in  the  proportion  of  10-25%  by 
volume  with  the  view  of  preventing  polymerisation  of  the  aldehyde,  especially 
in  concentrated  solutions  (about  40%).  Occasionally  the  methyl  alcohol  is 
replaced  by  other  products,  such  as  ordinary  alcohol,  acetone,  calcium  chloride, 
etc. 

HYDROGEN    PEROXIDE 

H2O2  =  34 

Colourless,  clear,  odourless  liquid.  With  permanganate  it  effervesces 
briskly,  liberating  oxygen  and  decolorising  the  permanganate.  When 
acidified  with  a  little  dilute  sulphuric  acid,  treated  with  a  few  drops  of 
potassium  chromate  and  shaken  with  ether,  the  latter  is  coloured  blue. 

Commercial  hydrogen  peroxide  almost  always  contains  various  impurities, 
especially  sulphuric,  hydrochloric,  nitric,  phosphoric,  silicic,  hydrofluoric 
and  hydrofluosilicic  acids  (free  and  combined),  aluminium,  iron,  calcium, 
barium,  magnesium,  alkalies  and  ammonia.  It  may  also  contain  traces 
of  arsenic,  and,  as  an  adulterant,  oxalic  acid.  The  following  determinations 
are  made. 

1.  Sulphuric,  Hydrochloric,  Nitric  and  Phosphoric  Acids. — These 
are  detected  by  the  usual  reagents. 

2.  Silica. — After  evaporation  of  the  sample,  the  residue  is  tested  for 
silica  in  the  ordinary  way. 

3.  Hydrofluosilicic  Acid. — The  liquid  is  evaporated  to  small  volume 
and  tested  with  potassium  chloride  (white,  gelatinous  precipitate). 

4.  Oxaiiic  Acid. — The    liquid  is  treated    with    excess    of  ammonia, 
rendered  acid  with  acetic  acid  and  tested  with  calcium  chloride. 

5.  Metals,  Alkaline  Earths,  Alkalies. — These  are  detected  by  the 
ordinary   reagents    (ammonia,    ammonium   sulphide,    ammonium   oxalate, 
sodium  phosphate,  etc.),  the  liquid  itself  or  its  evaporated  residue  being 
used.     Iron  may  be  detected  with  ammonium  thiocyanate. 

6.  Fixed  Residue. — 50  or  100  c.c.  are  evaporated  in  a  tared  dish  on 
a  steam-bath,  the  residue  being  dried  at  110°  and  weighed. 

7.  Acidity. — 10    c.c.    are    titrated  with  N/io-alkali    in    presence  of 
phenolphthalein. 

8.  Determination   of   the   Active   Oxygen. — By  active   oxygen   is 
meant  the  volume  of  oxygen  yielded  by  i  vol.  of  the  peroxide.     25  c.c.  of 
the  liquid  are  diluted  to  250  c.c.  and  10  c.c.  of  .this  solution  (=  i  c.c.  of 
the  peroxide)  are  diluted  with  100  c.c.  of  water,  acidified  with  4  c.c.  of 


HYDROSULPHITES  69 

sulphuric  acid  and  titrated  in  the  cold  with  permanganate.  With  a  solution 
of  5-65  grams  of  pure  potassium  permanganate  per  litre,  each  c.c.  corresponds 
with  i  vol.  of  oxygen  ;  using  N/io-permanganate,  i  c.c.  =  0-5596  vol 
of  oxygen  and  i  vol.  of  oxygen  =  0-3  gram  H2O2. 

* 
*  * 

Commercial  hydrogen  peroxide  usually  contains  3-3-6%  of  H2O2,  and  thus 
yields  10-12  vols.  of  oxygen.  Nowadays  solutions  of  30%  or  50%  or  even 
higher  concentrations  are  prepared,  these  giving  100,  160  or  more  vols,  of  oxygen. 
That  intended  for  bleaching  textiles  should  contain  only  traces  of  iron,  alumina 
and  barium1  ;  an  acidity  corresponding  with  1-5  gram  of  sulphuric  acid  per 
litre  (3  c.c.  of  N/io-alkali  per  c.c.)  is  allowable.2  Pure  hydrogen  peroxide  for 
pharmaceutical  purposes  should  be  neutral  or  neutralisable  by  2  or  3  drops  of 
baryta  and  on  evaporation  should  leave  not  more  than  0-5  gram  of  fixed  residue 
per  litre  ;  it  should  yield  not  less  than  12  vols.  of  oxygen  (Italian  Pharmacopoeia). 


HYDROSULPHITES 

These  are  products  used  in  dyeing  and  for  decolorising  sugar  syrups, 
etc.,  and  have  various  compositions  and  names,  such  as  Hydrosulphite, 
Rongalite,  Hyraldite,  Decroline  and  Blankite.  The  active  principle  of  these 
products  is  sodium  hydrosiilphite,  Na2S2O4,  or  sodium  hydro  sulphite- for- 
maldehyde or  sulphoxylate,  NaHSO2)  CH2O  +  2H2O,  or  the  corresponding 
zinc  salts.  The  action  is  regulated,  according  to  circumstances,  by  addition 
of  zinc  oxide,  lithopone,  smah1  quantities  of  catalytic  substances  (induline 
scarlet,  patent  blue,  etc.).  As  impurities  it  may  contain  especially  excess 
of  water,  bisulphite,  sulphite  and  sulphate.  The  value  depends  on  the 
content  in  active  principle  (hydrosulphite  or  sulphoxylate),  which  is  deter- 
mined as  follows  : 

Quantitative  Determination. — This  is  based  on  the  reducing  power 
of  the  hydrosulphites  on  indigo  :  i  part  of  sodium  hydrosulphite  corresponds 
with  1-505  of  pure  indigo  and  i  part  of  sodium  sulphoxylate  with  1-705 
of  indigo.  The  procedure  is  as  follows  : 

(a)  WITH  SODIUM  HYDROSULPHITE.  1^505  gram  of  purest  indigo  and 
9  grams  of  sulphuric  acid  (monohydrate)  are  heated  for  6  hours  at  40-50° 
with  occasional  shaking  ;  after  cooling,  the  mass  is  poured  into  watei,  the 
solution  filtered,  the  filter  thoroughly  washed,  and  the  filtrate  made  up 
to  i  litre. 

Next  5  grains  of  the  sample  of  hydrosulphite  are  dissolved  in  10  c.c. 
of  sodium  hydroxide  solution  (38-40°  Baume),  the  volume  being  then  made 
up  to  500  c.c.  with  recently  boiled  water  and  the  air  in  the  neck  of  the  flask 
replaced  by  illuminating  gas.  The  solution  is  then  drawn  (not  poured) 
into  a  burette. 

100  c.c.  of  the  indigo  solution  are  introduced  into  a  conical  flask 
with  a  three-holed  stopper  traversed  by  the  end  of  the  burette  con- 
taining the  hydrosulphite  solution,  by  a  gas  entry  tube  reaching  almost 
to  the  surface  of  the  liquid  and  by  an  exit  tube.  A  current  of  illuminating 

1  Sisley,  "  Sur  1'anal.  de  1'eau  oxyg."  in  Rev.  g&n.  des  mat.  colorantes,  1901,  p.  209, 
and  1904,   p.   164. 
*  Sisley,  loc.  cit. 


70  IODINE 

gas  is  passed  through  the  flask  and  the  hydrosulphite  solution  run  in,  gradu- 
ally and  with  shaking,  until  the  blue  colour  of  the  indigo  is  replaced  by 
a  greenish-yellow  colour.  Dividing  1000  by  the  number  of  c.c.  of  hydro - 
sulphite  solution  used,  the  percentage  of  Na2S2O4  in  the  substance  tested 
is  obtained. 

(b)  WITH  SODIUM  SULPHOXYLATE  (hydrosulphite- formaldehyde).  The 
indigo  solution  is  prepared  as  before,  but  with  1-705  grams  of  indigo.  To 
100  c.c.  of  this  solution  are  added  10  c.c.  of  glacial  acetic  acid  and  the  liquid 
heated  for  5  minutes,  illuminating  gas  being  passed  and  the  solution  titrated 
with  a  solution  of  the  sulphoxylate  (10  grams  per  litre)  as  before.  The 
percentage  of  NaHSO2,  CH2O  +  2H2O  is  obtained  by  dividing  1000  by 
the  number  of  c.c.  used. 

With  zinc  sulphoxylate,  14  grams  are  dissolved  in  cold  water  together 
with  90  grams  of  ammonium  chloride  and  60  c.c.  of  25%  ammonia,  the 
liquid  being  filtered  and  made  up  to  a  litre.  This  solution  is  used  for  the 
titration  of  100  c.c.  of  the  indigo  solution  (1-705  gram  per  litre),  to  which 
are  added  10  c.c.  of  acetic  acid,  as  above.  If  n  is  the  number  of  c.c.  of  the 
sulphoxylate  solution  used,  the  percentage  of  zinc  sulphoxylate  (ZnHS02, 
CH2O)2O  is  given  by  10930/14  X  n. 


IODINE 

I  —  126-92  (127) 

Crude  iodine  forms  small  crystals  or  brown  crystalline  masses,  while 
the  resublimed  product  is  in  dark  grey  rhomboidal  plates  with  metallic 
lustre  ;  when  heated  it  yields  violet  vapour.  It  dissolves  in  about  10 
parts  of  alcohol  and  is  soluble  in  carbon  disulphide  giving  a  violet  solution 
and  also  in  potassium  iodide  solution.  The  most  common  impurities  are 
moisture,  chlorine,  bromine,  cyanogen,  small  proportions  of  fixed  sub- 
stances, and  graphite.  The  tests  to  be  made  are  : 

1.  Moisture. — When  shaken  in  a  dry  glass  vessel,  moist  iodine  becomes 
attached  here  and  there  to  the  walls. 

To  estimate  the  moisture,  about  0-5  gram  of  the  iodine  is  placed  in  a  tube 
i  cm.  wide  and  6  cm.  long,  2-3  grams  of  powdered  silver  being  then  added 
and  the  whole  weighed  and  gently  heated  until  all  the  water  is  expelled 
(the  upper  layer  of  silver  should  remain  unchanged),  cooled  and  re  weighed. 

2.  Fixed  Substances. — i  gram  is  heated  slowly  in  a  porcelain  dish 
until  all  the  iodine  is  volatilised,  the  residue  being  weighed  and  examined 
(mineral  substances,  graphite). 

3.  Cyanogen,   Chlorine,    Bromine. — About    i    gram    of    the    well 
powdered  iodine  is  triturated  with  about  40  c.c.  of  water,  the  liquid  being 
decanted  off  and  divided  into  two  portions  : 

(a)  To  one  portion  is  added  sufficient  dilute  sodium  thiosulphate  to 
decolorise  it,  then  a  crystal  of  ferrous  sulphate,  two  drops  of  ferric  chloride 
and  a  little  soda  ;  after  heating,  the  liquid  is  acidified  with  hydrochloric 
acid.  In  presence  of  cyanogen,  a  coloration  or  precipitate  of  prussian  blue 
appears. 


(b)  The  other  is  rendered  alkaline  with  ammonia,  treated  with  excess 
of  silver  nitrate  solution,  shaken  and  filtered.  The  filtrate  is  then  acidified 
with  nitric  acid,  a  precipitate  being  formed  in  presence  of  chlorine  or  bromine 
but  only  an  opalescence,  and  that  not  immediate,  when  the  iodine  is  pure. 

4.  Quantitative  Determination  of  the  Iodine. — In  absence  of  appre- 
ciable proportions  of  chlorine  or  bromine,  it  is  sufficient  to  dissolve  a  given 
weight  (0-1-0-2  gram)  of  the  iodine  in  potassium  iodide  solution  (i  :  10) 
and  to  titrate  with  thiosulphate  solution  in  presence  of  starch  paste  (i  c.c. 
of  N/io-thiosulphate  —  0-0127  gram  of  iodine). 

In  presence  of  chlorine  and  bromine,  the  iodine  is  dissolved  in  sodium 
hydroxide  solution,  sodium  bisulphite  solution  and  ferric  chloride  being 
added  and  the  solution  acidified  with  hydrochloric  acid  ;  the  liquid  is  then 
distilled  in  a  suitable  apparatus  until  all  the  iodine  passes  over.  The  iodine 
is  collected  in  potassium  iodide  solution  and  titrated  with  thiosulphate.1 

Crude  commercial  iodine  may  contain  as  much  as  22%  of  moisture, 
and  usually  contains  74-94%  of  iodine.  Resublimed  iodine  should  contain 
99-100%. 

LEAD    ACETATE 

Pb(C2H302)2  +  3H20=379 

The  pure  salt  is  in  transparent,  colourless  crystals,  which  in  dry  air 
effloresce,  losing  water  and  acetic  acid  and  absorbing  carbon  dioxide.  The 
crude  salt  (pyrolignite  of  lead]  forms  yellowish  fused  masses  of  empyreumatic 
odour. 

The  pure  acetate  should  answer  to  the  tests  1-4 ;  in  the  crude  acetate 
the  content  of  acetic  acid  is  determined  as  in  5. 

1.  Solubility. — -i  part  in  5  parts  of  distilled  water  should  give  a  clear, 
colourless  solution. 

2.  Chlorides,    Sulphates. — The    i  :  20   solution   should  not   become 
turbid  with  either  silver  nitrate  or  barium  chloride,  even  on  standing. 

3.  Copper. — The    i  :  10    solution,    treated   with    excess   of   ammonia 
and  filtered,  should  give  a  colourless  liquid. 

4.  Iron,  Alkaline  Earth  and  Alkali  Metals. — The  i  :  20  solution 
treated  with  dilute  sulphuric  acid  (or  acidified  with  dilute  hydrochloric 
acid  and  treated  with  hydrogen  sulphide)  until  the  lead  is  completely  pre- 
cipitated, should  give  a  filtrate  which  leaves  no  appreciable  residue  on 
evaporation  and  ignition. 

5.  Determination  of  the  Acetic  Acid. — This  is  carried  out  as  in 
calcium  acetate   (q.v.),     i  c.c.   N-alkali  =0-379  gram  of  Pb(C2H3O2)2  + 
3H20. 

MAGNESIA  (Magnesium  Oxide) 

MgO  =  40-36  (40) 

Pure  magnesium  oxide  (Magnesia  calcinata)  is  a  light,  white,  amorphous 
powder  which  may  contain,  as  impurities,  magnesium  carbonate  and  small 

1  Topf's  method,  Zeitschr.  /.  analyt.  Chem.,  1887,  p.  288. 


72  MAGNESIA  (MAGNESIUM  OXIDE) 

proportions  of  extraneous  salts  (of  calcium,  alkalies,  heavy  metals).  Crude 
magnesia  (calcined  magnesite},  for  technical  uses,  is  in  lumps  or  powder  of 
colour  varying  from  reddish-white  to  brownish-grey  and  may  contain 
more  or  less  considerable  proportions  of  carbonates,  ferric  oxide,  alumina, 
lime,  silica  and  silicates. 

Analysis  of  pure  magnesia  comprises  essentially  tests  for  the  commoner 
impurities  (1-4)  ;  the  analysis  of  calcined  magnesite  necessitates  various 
quantitative  determinations,  especially  of  the  magnesium  oxide,  lime, 
iron,  carbonates  and  silica  (5-7). 

1.  Carbonates,   Insoluble   Substances. — i   gram,   suspended  in   10 
c.c.  of  water  and  treated  with  10  c.c.  of  dilute  hydrochloric  acid  (i  :  i)  should 
give,  in  the  hot,  a  clear  colourless  solution  without  evolution  of  gas. 

2.  Chlorides,    Sulphates. — The  nitric   acid    (i  :  10)   solution   should 
give  no  turbidity  with  silver  nitrate  or  barium  chloride. 

3.  Phosphates  (and  Arsenic). — About  2  grams,  dissolved  in  the  least 
possible  quantity  of  hydrochloric  acid  and  treated  with  40  c.c.  of  10% 
ammonium  chloride  solution  and  10  c.c.  of  ammonia  (D  =  0-910)  should 
give  no  turbidity,  even  after  12  hours. 

4.  Heavy  Metals,  Lime. — i  gram,  dissolved  in  dilute  hydrochloric 
acid,  should  not  be  coloured  blue  by  potassium  ferrocyanide  (iron)  and 
should  not  be  rendered  turbid  by  hydrogen  sulphide,  even  when  alkaline 
with  ammonia  (copper,  lead,  iron,  zinc)  ;    treated  with  a  large  excess  of 
ammonium  chloride  and  then  with  ammonia  and  ammonium  oxalate,  it 
should  not  become  turbid  even  after  12  hours  (lime). 

5.  Determination  of  the  Carbonates . — Use  is  made  of  one  of  the 
methods  indicated  for  the  determination  of  carbon  dioxide  in  limestones 
and  clays  (see  Cement  Materials). 

6.  Determination  of  the  Silica,  Iron,  Alumina  and  Lime. — 1-3 
grams  of  the  magnesia,  according  to  its  purity,  are  dissolved  in  cone,  hydro- 
chloric acid  (better,  in  aqua  regia)  in  the  hot,  the  solution  being  evaporated 
to  dryness  and  the  residue  heated  at  110°,  taken  up  in  hydrochloric  acid 
and  filtered.     The  insoluble  part  remaining  on  the  filter,  after  washing, 
igniting  and  weighing,  gives  the  silica. 

To  the  filtrate  are  added  excess  of  ammonium  chloride  and  slight  excess 
of  ammonia  to  precipitate  the  iron  and  aluminium,  which  are  weighed  as 
oxides  in  the  usual  way.  In  the  filtrate  from  this  precipitate  the  lime  is 
precipitated  with  ammonium  oxalate,  which  is  redissolved  in  dilute  hydro- 
chloric acid  and  again  precipitated  with  ammonium  chloride,  ammonia  and 
ammonium  oxalate  ;  in  this  way  the  precipitate  is  freed  from  magnesia. 

7.  Determination  of  the  Magnesia.— With  calcined  magnesite  the 
total  magnesia  or  that  existing  as  oxide  is  required. 

(a)  TOTAL  MAGNESIA  (Meyerhofer's  method).  5  grams  of  the  finely 
powdered  sample  are  evaporated  to  dryness  with  aqua  regia  on  a  steam- 
bath,  the  residue  heated  in  an  oven  at  180-200°  for  30  minutes  and  redis- 
solved in  a  little  hot  hydrochloric  acid,  and  the  solution  filtered  and  the 
filtrate  made  up  to  i  litre.  ' 

Of  this  solution,  20  c.c.  (=  i  gram  of  substance)  are  treated  in  a  beaker 
successively  with  5  c.c.  of  concentrated  sulphuric  acid,  100  c.c.  of  ammoniacal 


73 

citric  acid  solution  (100  grams  of  citric  acid  and  333  c.c.  of  ammonia,  of 
D  =  0-910  to  i  litre),  20  c.c.  of  10%  sodium  phosphate  and  15  c.c.  of  cone, 
ammonia  solution  (in  this  way  the  magnesia  alone  is  precipitated  as  mag- 
nesium ammonium  phosphate,  the  other  bases  remaining  in  solution).  The 
liquid  is  well  stirred  for  5  minutes,  left  to  stand  for  2  hours  and  filtered 
(best  through  a  Gooch  crucible),  the  precipitate  being  washed,  calcined 
and  weighed  as  pyrophosphate  ;  this  weight,  multiplied  by  360,  gives  the 
percentage  of  MgO. 

(b)  MAGNESIUM  AS  OXIDE  (Fortini's  method).1  This  method  requires 
a  small  calorimeter  with  a  chamber  unattackable  by  hydrochloric  acid  and 
an  accurate  thermometer  ;  Tortelli's  thermo-oleometer,  described  under 
"  Fatty  Substances  "  (General  Methods,  21),  serves  excellently  for  this 
purpose. 

In  the  chamber  of  the  thermo-oleometer  are  placed  25  c.c.  of  hydro- 
chloric acid  (equal  volumes  of  acid  D  =  1-19  and  water),  and  after  a  few 
moments  the  temperature  shown  by  the  thermometer  stirrer  noted.  An 
exactly  weighed  amount  of  the  magnesia  (0-5-1-0  gram)  is  then  added  and 
well  mixed  in  until  the  temperature  no  longer  rises.  The  total  rise  of  tem- 
perature is  proportional  to  the  heat  of  the  reaction,  when  a  given  calorimeter 
and  a  given  quantity  of  acid  are  used.  With  Tortelli's  thermo-oleometer 
and  the  above  quantity  of  hydrochloric  acid,  i  gram  of  MgO  gives  a  rise 

of  37°. 

The  carbonates  and  other  impurities  of  calcined  magnesites  give  no 
appreciable  rise  of  temperature  on  reaction  with  hydrochloric  acid,  but 
calcium  oxide  behaves  exactly  like  magnesium  oxide. 

* 

*   * 

Pure  magnesia  for  pharmaceutical  purposes  or  for  chemical  laboratories 
should  correspond  with  tests  1-4.  Calcined  magnesite  for  making  magnesia 
cements,  dielectric  or  insulating  materials,  artificial  stone,  etc.,  should  contain 
little  carbonate  (losing  not  more  than  5%  on  calcination),  not  more  than  4% 
of  calcium  oxide  and  85-90%  of  magnesium  oxide.  That  for  metallurgical 
use  (refractory  materials)  does  not  contain  carbonates  and  may  contain  marked 
quantities  of  ferric  oxide  (up  to  10%),  as  well  as  manganese  oxide,  lime,  alumina 
and  silica. 

MAGNESIUM    CHLORIDE 

MgCl2  +  6H2O  =  203-34 

Colourless,  deliquescent  crystals,  soluble  in  water  or  alcohol.  It  may 
contain  sulphates  and  sodium  salts  more  especially,  and  sometimes  phos- 
phates, heavy  metals,  lime  and  ammonia,  these  being  tested  for  thus  : 

1.  Solubility. — 3  grams  should  give  a  clear  solution  with  15  c.c.  of 
absolute  alcohol  if  the  salt  is  pure  ;    any  insoluble  residue  is  tested  for 
sodium  salts. 

2.  Sulphates. — The  i  :  10  solution,  acidified  with  hydrochloric  acid,  is 
tested  with  barium  chloride. 

3.  Phosphates. — 2  grams,   dissolved  in  40  c.c.   of  10%  ammonium 

1  Ann.  Lab.  Chim.  Gabelle,  Vol.  VI,  p.  509. 


74 

chloride  solution,  are  treated  with  6  c.c.  of  ammonia  and  any  turbidity 
formed  within  12  hours  noted. 

4.  Heavy  Metals,  Lime. — The  i  :  20  solution  is  treated  with  hydrogen 
sulphide  and  any  turbidity  noted,  either  before  or  after  addition  of  ammonia 
(heavy  metals). 

The  same  solution  is  treated  wtih  ammonium  chloride  in  excess  and 
then  with  ammonium  oxalate  (lime). 

5.  Ammonia. — See  Stannic  Chloride. 


MAGNESIUM    SULPHATE 

MgS04  +  7H20  =  246-32 

Colourless  crystals,  readily  soluble  in  1-5  parts  of  water.  It  may  be 
contaminated  with  chlorides,  phosphates,  arsenic,  copper,  iron,  zinc,  alu- 
minium, lime  and  alkalies. 

1.  Solubility,  Chlorides. — The  aqueous  solution  should  be  clear  and 
neutral  and  should  not  become  milky  with  silver  nitrate. 

2.  Phosphates. — 5  grams,  dissolved  in  35  c.c.  of  water  and  treated 
with  ammonium  chloride  and  excess  of  ammonia,  should  give  a  limpid 
solution  even  after  standing  for  hours. 

3.  Arsenic. — -I  gram,  treated  with  5  c.c.  of  Bettendorf's  reagent,  should 
not  colour  within  an  hour. 

4.  Metals,  Earths. — The  i  :  10  solution  should  not  change  with  hydro- 
gen sulphide,  or  ammonia,  or  ammonium  sulphide,  or  ammonium  oxalate, 
or  potassium  ferrocyanide. 

5.  Alkalies. — i  gram,  dissolved  in  30  c.c.  of  water,  is  boiled  with  3 
grams  of  barium  carbonate  and  filtered  :    the  filtrate  should  not  react 
alkaline  and  should  leave  no  appreciable  residue  on  evaporation. 


MANGANESE    DIOXIDE 

MnO2  =  86-93  (87) 

The  product  of  this  composition  of  the  greatest  practical  importance 
is  the  natural  Pyrolusite,  which  forms  compact  masses  or  small  irregular 
pieces  or  more  or  less  coarse  powder.  The  mass  has  a  radiating  crystalline 
structure,  a  greyish-brown  colour  and  an  almost  metallic  lustre  ;  the  powder 
is  black. 

Pyrolusite  often  occurs  mixed  with  other  oxides  of  manganese,  such  as 
Bmunite,  manganic  oxide ;  Hausmannite,  mixed  manganous-manganic 
oxide ;  Manganite,  hydrated  manganic  oxide ;  Psilomelan,  manganous 
oxide  and  manganese  dioxide. 

These  minerals  may  contain  also  variable  quantities  of  ferric  oxide, 
alumina,  baryta,  magnesia  and  silica  (gangue),  and  small  amounts  of  lead 
or  copper  oxide,  lime,  alkalies,  sulphates,  phosphates  and  chlorides. 

The  value  of  the  pyrolusite  and  of  the  other  minerals  depends  on  the 


MANGANESE  DIOXIDE  75 

content  of  MnO2)  determination  of  which  is  the  principal  aim  of  the  analysis  ; 
the  latter  may,  however,  be  extended  to  the  determination  of  moisture, 
total  manganese,  carbon  dioxide  and  any  other  extraneous  matters. 

1.  Moisture. — 1-2  grams  of  the  finely  powdered  substance  are  dried 
at  100°  for  6  hours. 

2.  Determination  of  the  Manganese  Dioxide  (Lunge's  method). — 
i -0866  gram  of  the  dry  substance  is  mixed,  in  a  300  c.c.  flask  furnished  with 
a  Bunsen  valve  (see  Limestones  and  Clays),  with  75  c.c.  of  ferrous  sulphate 
solution  (100  grams  of  the  pure  sulphate  or  the  corresponding  quantity  of 
ferrous  ammonium  sulphate,  and  100  c.c.  of  cone,  pure  sulphuric  acid  in 
i  litre),  the  titre  of  which  has  been  recently  determined  with  N/2-perman- 
ganate  (15-815  grams  of  pure  permanganate  per  litre).     The  flask  is  closed 
and  heated  until  all  the  pyrolusite  is  acted  on,  that  is,  until  no  brown  deposit 
remains.     When  cool,  the  liquid  is  diluted  with  about  200  c.c.  of  boiled 
water  and  titrated  with  the  permanganate  solution  until  the  pink  coloration 
persists  for  half  a  minute.     The  difference  between  the  number  of  c.c.  of 
permanganate  used  to  titrate  the  75  c.c.  of  the  ferrous  solution  and  that 
used  in  the  test  gives,  when'  multiplied  by  2,  the  percentage  of  Mn02  in 
the  substance  (i  c.c.  of  the  KMnO4  =0-02173  gram  of  MnO2).- 

3.  Determination  of  the  Total  Manganese. — 1-0875  gram  is  treated 
with  cone,  hydrochloric  acid  until  evolution  of  chlorine  ceases,  the  excess  of 
acid  being  neutralised  with  pure,  precipitated  calcium  carbonate  and  con- 
centrated, filtered  chloride  of  lime  solution  added  ;    after  heating  for  a 
few  minutes  the  liquid  is  decolorised  by  addition  of  alcohol,  drop  by  drop. 
The  whole  of  the  manganese  is  then  precipitated  as  dioxide  (the  filtrate 
should  not  turn  brown  on  further  addition  of  chloride  of  lime).     The  pre- 
cipitate is  filtered  off  and  washed  until  the  wash-water  no   longer  colours 
starch-iodide  paper,  and  is  then  treated  with  ferrous  sulphate  as  in  2.    The 
manganese  is  calculated  as  Mn02. 

4.  Carbon  Dioxide. — This  is  determined  as  in  chalk  (see  Chapter  on 
Cement  Materials). 

5.  Other  Tests. — For  the  detection  and  determination  of  the  various 
foreign  substances   (see  above)  the  ordinary  analytical  methods  may  be 
followed.     Tests  are  made  more  particularly  for  oxides  of  iron  and  other 
metals,  lime,  baryta,  silica  and  phosphoric  acid. 

In  general,  pyrolusite  contains  35-85%  MnO2  (the  purer,  well  crystallised 
product  may  contain  about  90%).  The  qualities  to  be  used  for  making  chlorine 
should  contain,  if  of  German  origin,  not  less  than  60%  MnO2,  or,  if  of  Spanish 
origin,  not  less  than  70%.  Extraneous  matters  may  be  present  in  the  follow- 
ing proportions  :  ferric  oxide,  up  to  30%  ;  alumina,  up  to  4%  ;  lime,  up  to  4%  ; 
silica,  up  to  20%  ;  and  phosphoric  acid,  up  to  i%.  The  manganese  minerals 
for  the  manufacture  of  glass  should  be  free  from  coloured  oxides  (iron,  nickel, 
cobalt,  copper)  ;  those  for  the  treatment  of  iron  or  steel  should  not  contain 
heavy  spar,  sulphides,  copper,  nickel,  cobalt  or  phosphorus,  and  should  be  poor 
in  silica. 


76  MERCURIC  CHLORIDE 

MERCURIC    CHLORIDE  (Corrosive  Sublimate) 

HgCl2  —  270-98  (271) 

White  crystals  or  crystalline  masses  soluble  in  about  16  parts  of  water 
(at  15°),  in  2-5  parts  of  90%  alcohol,  or  in  14  parts  of  ether.  It  may  contain 
as  impurities,  salts  of  sodium,  manganese,  zinc  or  other  extraneous  metals, 
arsenic  and  calomel.  The  mercuric  chloride,  especially  in  basic  preparations 
of  the  salt,  is  determined  as  in  4. 

1.  Impurities  in  general. — i  gram,  dissolved  in  10  c.c.  of  water  and 
acidified  with  HC1,  is  treated  with  excess  of  hydrogen  sulphide  :   with  the 
pure  salt,  a  black  precipitate  and  a  colourless  liquid  are  obtained,  the  latter 
leaving  no  appreciable  residue  (alkali  or  alkaline  earth  salts,  etc.)  on  evapora- 
tion. 

2.  Arsenic. — The  sulphide  precipitate  from  i  is  treated  with  dilute 
ammonia  and  filtered  ;   the  filtrate  should  not  give  a  yellow  colour  or  pre- 
cipitate on  acidification  with  hydrochloric  acid. 

3.  Calomel. — i  gram  should  dissolve  completely  in  alcohol  or  ether. 

4.  Quantitative  Determination. — The  estimation  of  mercuric  chloride 
in  sublimate  pastilles,  cotton  wool,  gauze  and  other  antiseptic  preparations 
is  carried  out  as  follows  : 

(a)  IODOMETRIC  METHOD.     2-3  grams  of  the  sublimate  or  pastilles  are 
dissolved  in  water  to  500  c.c.     With  cotton  wool,  gauze  or  other  similar 
material,  which  usually  contains  about  0-5%  of  the  chloride,  20-25  grams 
are  digested  for  some  hours  with  water,  pressed  out  well  and  washed,  the 
liquid  being  filtered  and  made  up  to  500  c.c.     An  aliquot  part  of  this  solu- 
tion, containing  o-o5-o-io  gram  of  sublimate,  is  acidified  with  a  little  hydro- 
chloric acid  and  precipitated  in  the  hot  with  hydrogen  sulphide.     The 
mercuric  sulphide  is  filtered  off,  washed  and  introduced,  with  the  paper, 
into  a  bottle  with  ground  stopper ;   a  little  water  (20-25  c.c.),  about  5  c.c. 
of  carbon  disulphide  and  excess  of  N/io-iodine  (20-25  c.c.  usually  suffice) 
are  added,  the  bottle  shaken  vigorously  and  the  excess  of  iodine  titrated 
with  N/io-sodium  thiosulphate  in  presence  of  starch  paste.1    The  differ- 
ence between  the  number  of  c.c.  of  iodine  solution  added  and  the  number 
of  c.c.  of  thiosulphate  necessary  to  act  on  the  excess  of  iodine,  gives,  when 
multiplied  by  0-01356,  the  mercuric  chloride  in  the  volume  of  solution 
taken  for  the  determination. 

(b)  ALKALIMETRIC   OR   HYDRAZINE   METHOD,2   adapted   especially   for 
analysis  of  corrosive  sublimate  pastilles  or  compresses.     A  pastille  is  dis- 
solved in  a  little  hot  water  and  to  the  solution  are  added  20  c.c.  of  cold 
saturated  hydrazine  sulphate  solution  previously  neutralised  to  methyl 
orange,  and  exactly  10  c.c.  of  N-sodium  hydroxide  ;  the  liquid  is  shaken, 
left  for  a  few  minutes,  and  filtered,  the  filter  being  well  washed  with  hot 
water  and  the  excess  of  sodium  hydroxide  in  the  filtrate  titrated  with  N/io- 

1  The  mercuric  sulphide  reacts  with  iodine  in  potassium  iodide  solution,  thus  : 
HgS  +  2!  +2KI  =  HgI2  +  2KI  +  S.     Carbon  disulphide  is  added  in  order  to  dissolve 
the  sulphur  liberated  in  this  reaction. 

2  According  to  Rimini,  Rend.  R.  Accad.  Lincei,  XV,  2,  p.  323,  and  Boll.  chim.  farm,, 
1908,  p.   145. 


CHROME  MORDANTS  77 

sulphuric  acid  in  presence  of  methyl  orange,     i  c.c.  N-NaOH  =  0-1084 
gram  HgCl2. 


MERCUROUS    CHLORIDE 

Hg2Cl2  =  470-9 

A  white  powder,  insoluble  in  water,  alcohol  or  ether.  It  is  sold  as  : 
Sublimed  calomel,  transparent  crystals  under  the  microscope ;  calomel 
condensed  in  steam,  particles  which  are  opaque  or  at  most  transparent  at 
the  edges  ;  Precipitated  calomel,  formed  of  very  minute,  amorphous  opaque 
particles  (when  the  salt  is  finely  triturated,  these  microscopic  characters 
are  no  longer  discernible).  As  impurities  or  adulterants  there  may  appear 
mercuric  chloride,  mercuric  aminochloride  (white  precipitate),  sodium 
chloride,  barium  sulphate,  kaolin,  lead  carbonate,  gypsum,  chalk,  etc. 

1.  Fixed  Substances. — i  gram,  heated  in  a  porcelain  crucible,  should 
yield  no  appreciable  residue  if  pure. 

2.  Mercuric  Chloride. — -i  gram  is  shaken  with  10  c.c.  of  water  and 
filtered,  the  filtrate  being  tested  with  silver  nitrate  and  with  hydrogen 
sulphide  ;    with  the  former  scarcely  any  milkiness  and  with  the  latter  a 
faint  brown  ccloration  are  allowable. 

3.  White  Precipitate. — The  sample  is  heated  with  excess  of  caustic 
potash  solution  ;    in  presence  of  white  precipitate,  ammonia  is  evolved. 


CHROME    MORDANTS 

The  chromium  compounds  used  in  dyeing  and  tanning  include,  besides 
chromic  acid  and  sodium  and  potassium  chromates  and  dichromates  (see 
separate  articles),  the  following  : 

Chromium  acetate,  either  neutral,  Cr(C2H3O2)3,  or  basic,  CrOH(C2H3O2)2, 
in  green  or  violet  solution  of  20°,  24°  and  30°  Baume  or  in  the  dry  state. 
Chromium  Sulphoacetate  and  Nitroacetate,  which  are  mixtures  of  the  acetate 
with  the  sulphate  or  nitrate  of  chromium  in  various  proportions. 

Chromium  chloride,  in  solution  of  20-30°  Baume,  usually  containing 
basic  chlorides,  CrCl(OH)2,  CrCl2(OH)  and  Cr2C]3(OH)3,  and  often  con- 
taminated with  alkali  salts,  sulphates  and  iron. 

Chromic  fluoride,  CrF3  +  4H2O,  in  green  crystals  or  powder. 

Chromic  formate,  Cr(HCO2)3  or  CrOH(HCO2)2,  in  green  solution. 

Chromic  hydroxide,  Cr(OH)3)  in  greyish -green  paste  or  powder. 

Chromic  sulphate,  Cr2(SO4)3  +  I5H2O  ;  basic  sulphates  of  various  com- 
positions ;  chromium  and  potassium  sulphate  or  chrome  alum,  Cr2(SO4)3, 
K2SO4  +  24H2O,  in  dark  reddish -violet  crystals  ;  mixtures  in  various 
proportions  of  more  or  less  basic  chromium  sulphate  with  sodium  sulphate 
(often  also  with  the  formate)  either  in  green  solution  or  in  small  green, 
apparently  crystalline  fragments.  All  these  sulphates  may  be  contami- 
nated with  gypsum,  free  sulphuric  acid  and  tarry  matters. 

Analysis  of  these  products  includes  investigation  of  the  bases  and  acids 


78  IRON   MORDANTS 

and  of  any  impurities  (especially  iron),  which  are  detected  by  the  ordinary 
methods,  and  especially  determination  of  the  chromium,  for  which  the 
two  following  methods  serve  : 

(a]  GRAVIMETRIC.    The  substance   (5-10  grams  of  a  solution  or  1-2 
grams  of  a  solid)  is  diluted  with  or  dissolved  in  water  (the  hydroxide  in 
hydrochloric  acid),   excess  of  ammonium   chloride  or  nitrate  and   slight 
excess  of  ammonia  being  added  and  the  solution  boiled  until  the  liquid 
above  the  precipitate  is  quite  decolorised.     After  nitration,  the  precipitate 
is  washed  with  water  containing  ammonium  nitrate,  dried,  ignited  and 
weighed  as  Ci203;    i  part  of  Cr203  —0-6853  Pai"t  Cr. 

(b)  VOLUMETRIC.     10  grams  of  solution  (or  i  gram  of  solid)  are  dis- 
solved in  water  or  hydrochloric  acid  and  the  volume  made  up  to  100  c.c.  ; 
10  c.c.  (=  i  gram  of  original  solution  or  o-i  gram  of  a  solid  salt)  are  treated 
in  a  litre  porcelain  dish  with  concentrated  sodium  hydroxide  solution  until 
the  precipitate  initially  formed  redissolves.      The  dish  is  then  heated  on  a 
steam-bath  and  sodium  peroxide  added  in  small  amounts  until  a  perfectly 
yellow  solution  is  obtained  (the  chromium  being  transformed  into  chro- 
mate),.1    The  liquid  is  then  evaporated  to  dryness,  the  residue  taken  up 
in  water,  and  the  dichromate  in  the  solution  estimated  iodometrically  as 
described  under  Potassium  Dichromate  (5,  b)  :   i  c.c.  of  N/io-thiosulphate 
=  0-002533  gram  of  Cr2O3. 

If  the  basicity  of  the  chromium  salt  is  desired,  the  acid  must  be  deter- 
mined and  the  amount  of  acid  corresponding  with  i  part  of  chromium  (see 
Aluminium  Sulphate,  3)  calculated. 

IRON    MORDANTS 

These  include  the  sulphate  and  acetate  (see  separate  articles)  and  solu- 
tions of  Basic  ferric  sulphate  and  Ferric  nitrate,  which  are  known  as  iron 
mordant  or  fenugine.  These  solutions  are  reddish-brown  liquids  of  D  1-35- 
1-56,  corresponding  with  40-52°  Baume,  and  they  contain,  besides  ferric 
sulphate  or  nitrate  or  both  of  these  salts,  also  ferrous  and  alkali  salts.  These 
products  are  analysed  as  follows  : 

1 .  Nature  of  the  Mordant. — -The  dilute  solution  is  treated  with  hydro- 
chloric acid  and  barium  chloride  ;   if  sulphate  is  present  an  abundant  white 
precipitate  of  barium  sulphate  is  formed.     A  second  portion  of  the  solution 
is  evaporated  to  dryness  on  the  water-bath  and  the  residue  treated  with  a 
few  pieces  of  copper  and  cone,  sulphuric  acid  :   if  nitrate  is  present,  evolu- 
tion of  red  vapours  occurs. 

2.  Iron. — 10  grams  of  the  substance  are  diluted  to  100  c.c.  with  water 
and  10  c.c.  of  this  solution  (=  i  gram  of  substance)  boiled  with  a  few  drops 
of  nitric  acid   the  iron  being  then  precipitated  with  ammonia  and  weighed 
as  ferric  oxide,   this  gives  the  total  iron   (i   part  Fe2O3=o-7  part  Fe). 
Another  aliquot  part  of  the  dilute  solution  is  acidified  with  pure  sulphuric 

1  If  the  product  to  be  analysed  contains  organic  salts  or  substances,  it  should  be 
fused  with  solid  sodium  hydroxide  (1-2  grams)  in  a  nickel  crucible  and  a  small  quantity 
of  sodium  peroxide  then  added.  After  cooling,  the  mass  is  dissolved  in  water  and  the 
dichromate  in  the  solution  determined  iodometrically. 


79 

acid  and  titrated  with  N/io-permanganate  ;    this  gives  the  iron  in  the 
ferrous  state  (i  c.c.  N/io-permanganate  =  0-0056  gram  Fe). 

3.  Sulphuric  Acid. — The  filtrate  from  the  total  iron  precipitate  is 
acidified  with  hydrochloric   acid  and  precipitated  with  barium   chloride 
(i  part  BaSO4  =  0-3433  part  SO3). 

4.  Nitric  Acid. — This  may  be  determined  by  one  of  the  methods  given 
under  "  Fertilisers." 

5.  Alkalies. — In  absence  of  lime  and  magnesia  (the  usual  case),  it  is 
sufficient  to  precipitate  the  iron  with  ammonia  as  in  2,  to  filter,  evaporate 
the  filtrate  to  dryness  with  a  few  drops  of  sulphuric  acid,  and  calcine  and 
weigh  the  residue  :   assuming  the  latter  to  be  sodium  sulphate,  the  alkalies 
are  calculated. 


NITROBENZENE 

C6H6-N02  =  123 

This  is  sold  in  various  qualities  :  (i)  Pure  light  nitrobenzene  (Essence  of 
mirbane],  a  colourless  or  yellowish  liquid  with  a  pleasant  odour  of  bitter 
almonds,  D  =  1-208-1-209,  b.pt.  205-207°.  (2)  Crude  heavy  nitrobenzene 
(Nitrobenzene  for  red],  a  reddish  liquid  smelling  of  bitter  almonds  and  tarry 
products,  D  =  1-18-1-19,  b.pt.  210-220°  ;  it  contains  nitrotoluenes  and 
other  homologues.  (3)  Extra  heavy  nitrobenzene,  a  brownish-red  liquid, 
D  =  1-167,  b.pt.  220-240°,  containing  little  nitrobenzenes  and  much  nitro- 
toluenes, nitroxylenes,  etc. 

With  these  products  the  determinations  usually  made  are  those  of  the 
specific  gravity  and  the  boiling  point. 

Nitrotoluene  may  be  detected  in  pure  nitrobenzene  by  shaking  a  few 
c.c.  of  the  product  with  1-2  grams  of  powdered  sodium  (not  potassium) 
hydroxide  :  in  presence  of  nitrotoluene,  even  in  very  small  amounts,  the 
liquid  becomes  brownish  yellow. 

Pure  nitrobenzene  should  have  a  specific  gravity  not  less  than  1-20  (at  15°), 
and  at  least  95%  of  it  should  distil  between  204°  and  208°. 


POTASSIUM    ALUMINIUM    SULPHATE— see  Alum 

POTASSIUM    BISULPHITE 

KHSO3  =  120 

This  usually  forms  slightly  effloresced  crystalline  masses,  very  readily 
soluble  in  water  to  an  acid  solution.  It  may  contain  the  same  impurities 
as  sodium  bisulphite  and  its  value  depends  on  its  proportion  of  sulphur 
dioxide.  Its  analysis  is  carried  out  similarly  to  that  of  the  sodium  salt. 

Commercial  potassium  bisulphite  is  also  called  metabisulphite,  and  is  probably 
a  mixture  of  the  normal  bisulphite,  KHSO3,  and  the  metabisulphite,  K2S2O5.  It 
contains  about  53%  of  total  SO2. 


8o  POTASSIUM  BROMIDE 

POTASSIUM    BITARTRATE  (Cream  of  Tartar) 

KC4H5O6  =  188-2 

The  impure  salt  constitutes  crude  tartar  (see  p.  36).  The  pure  or  refined 
product  forms  white  rhombic  crystals  or  crystalline  powder  and  dissolves 
in  about  220  parts  of  cold  water  or  15  parts  of  boiling  water,  but  is  insoluble 
in  alcohol. 

It  may  be  contaminated  with  small  proportions  of  calcium,  lead,  copper 
or  iron  salts,  or  adulterated  with  various  mineral  salts  (alum  or  other  acid 
salt).  Its  analysis  includes  the  following  : 

1.  Insoluble  Substances. — i  gram  is  either  treated  with  220  c.c.  of 
water  at  the  ordinary  temperature  or  boiled  with  18  c.c.  of  water.     If  the 
salt  is  pure,  a  clear  solution  should  be  obtained  in  either  case  ;  any  insoluble 
residue  left  is  tested  especially  for  calcium  tartrate,  calcium  carbonate, 
gypsum,  clay,  etc. 

2.  Nitrates,  Sulphates,  Chlorides. — 10  grams  are  heated  to  boiling 
with  30  c.c.  of  water,  cooled  and  filtered,  the  filtrate  being  tested  with  the 
ordinary  reagents  for  these  radicles. 

3.  Heavy   Metals. — 5   grams  are   dissolved  in  ammonia,   the  liquid 
being  acidified  with  hydrochloric  acid  and  treated  with  hydrogen  sulphide, 
then  with  ammonium  sulphide,  etc.,  according  to  the  ordinary  method  of 
analysis. 

4.  Calcium  Tartrate  (small  quantities). — i  gram  is  treated  in  the  hot 
with  10  c.c.  of  water  and  a  few  drops  of  ammonia  until  solution  occurs  : 
ammonium  oxalate  should  give  no  turbidity. 

5.  Quantitative  Determination. — 0-5   gram  is  dissolved  in   boiling 
water  (100  c.c.)  and  titrated  with  normal  alkali  in  presence  of  phenolphtha- 
lein.     i  c.c.  N-alkali  =  0*1882  gram  of  potassium  bitartrate. 


POTASSIUM    BROMIDE 

KBr  =  119 

White,  deliquescent  crystals,  highly  soluble  in  water.  It  may  be  con- 
taminated by  bromates,  sulphates,  chlorides,  iodides  and  carbonates.  The 
tests  and  determinations  made  are  as  follows  : 

1.  Sulphates,    Metals,    Alkaline   Earths. — The    i  :  10    solution    is 
tested  with  barium  nitrate  (sulphates),  hydrogen  sulphide  (heavy  metals), 
ammonia,  ammonium  sulphide  and  ammonium  oxalate.     Sodium  is  detected 
by  the  flame  test  or  by  potassium  pyroantimoniate. 

2.  Carbonates. — No    effervescence   should    be    obtained   with    dilute 
hydrochloric  acid.     A  crystal  placed  on  red  litmus  paper  and  moistened 
with  a  drop  of  water  gives  a  blue  stain  if  alkali  carbonate  is  present. 

3.  Bromates. — o-i  gram,  moistened  with  very  dilute  sulphuric  acid, 
should  not  turn  yellow  or  emit  an  odour  of  bromine. 

4.  Iodides. — 0-5  gram,  dissolved  in  5  c.c.  of  water,  is  treated  witli  a 
drop  of  ferric  chloride  solution  or  a  few  crystals  of  potassium  nitrite  and  a 


POTASSIUM  CARBONATE  81 

few  drops  of  dilute  sulphuric  acid  and  shaken  with  chloroform  ;  the  latter 
is  coloured  violet  in  presence  of  iodides. 

5.  Chlorides. — 0-5  gram  is  dissolved  in  30  c.c.  of  water  and  5  c.c.  of 
this  solution,  acidified  with  nitric  acid,  treated  with  silver  nitrate  until 
precipitation  is  complete  ;  the  precipitate  is  washed  several  times  by  decan- 
tation  and  then  digested  with  4  c.c.  of  ammonium  carbonate  solution  (i  :  6) 
and  filtered  :   the  filtrate,  acidified  with  nitric  acid,  should  give  at  most  a 
faint  milkiness. 

6.  Quantitative  Determination. — 10  c.c    of  a  solution  of  3  grams 
of  the  bromide,  dried  at  100°,  in  100  c.c.  of  water,  are  titrated  with  N/io- 
silver  nitrate  in  presence  of  potassium  chromate.     The  red  colour  should 
be  obtained  with  25-2  c.c.  of  the  silver  solution,  if  the  bromide  is  pure. 
If  chlorides  are  present,  a  larger  quantity  is  required. 

The  volume  permitted  by  the  Italian  Pharmacopoeia  is  25-4  c.c.  of  the  N/io- 
silver  solution. 

POTASSIUM    CARBONATE 

K2C03  =  138-2  (138) 

Crude  potassium  carbonate  (crude  potash)  forms  reddish  or  bluish  grey, 
spongy  masses,  deliquescent  in  moist  air.  Its  impurities  are  more  particu- 
larly water,  chlorides,  sulphates,  sulphites,  sulphides,  phosphates,  cyanogen 
compounds,  potassium  hydroxide,  sodium  carbonate  and  insoluble  matter. 
Its  analysis  includes  determinations  of  the  insoluble  matter,  carbonate, 
hydroxide,  chloride,  sulphate  and  sulphide  (sulphite),  which  are  carried 
out  as  in  sodium  carbonate  (q.v.),  and  also  of  the  water,  phosphates  and 
sodium  salts  (see  below).1 

Commercial  pure  potassium  carbonate  (refined  potash)  occurs  in  powder, 
or  in  hygroscopic,  white  crystalline  crusts  extremely  soluble  in  water. 
According  to  the  degree  of  refining,  it  may  contain  more  or  less  marked 
proportions  of  chloride,  sulphate,  phosphate,  silicate,  insoluble  substances 
and  moisture,  which  are  investigated  as  described  under  "  Caustic  Potash," 
and  are  determined  as  in  crude  potash. 

The  chemically  pure  carbonate  (puriss.)  should  contain  only  traces  of 
chloride  and  sulphate  and  is  tested  like  potassium  hydroxide  (q.v.). 

1.  Water. — 10  grams  are  heated  to  redness  in  a  platinum  crucible,  the 
loss  representing  water. 

2.  Phosphates. — 5  grams  are  dissolved  in  nitric  acid  and  filtered,  the 
filtrate  being  heated  and  precipitated  with  ammonium  molybdate ;  the 
precipitate  is  dissolved  in  ammonia,  precipitated  with  magnesia  mixture 

(see  Fertilisers)  and  the  magnesium  ammonium  phosphate  filtered,  ignited 
and  weighed  as  magnesium  pyro phosphate  in  the'ordinary  way.  Mg2P207 

X  1-907  =  K3PO4. 

3.  Sodium  Salts. — TO  c.c.  of  the  10%  solution  of  the  carbonate  (=i 
gram  of  substance)  are  exactly  neutralised  with  N-hydrochloric  acid  (to 
methyl  orange),  heated  to  expel  carbon  dioxide  (and  any  sulphur  dioxide 

1  For  the  Rapid  Analysis  of  Potassium  Carbonate,  see  also  E.  Baroni  in  L'Industria 
chimica,  1904,  VI,  p.  164. 

A.C.  6 


82  POTASSIUM  CHLORATE 

or  hydrogen  sulphide)  and  normal  barium  chloride  solution  added  in  amount 
exactly  equivalent  to  the  potassium  sulphate  (also  to  any  phosphate  present) 
already  found  by  another  way.  The  liquid  is  heated  and  filtered,  the 
insoluble  matter  washed,  the  filtrate  evaporated  to  dryness  and  the  residue 
carefully  ignited,  taken  up  in  a  little  water  and  a  few  drops  of  ammonium 
carbonate,  the  solution  filtered  if  necessary  and  evaporated  in  a  tared 
platinum  dish,  the  residue  being  gently  ignited  and  weighed.  In  the  pure 
chlorides  thus  obtained  the  chlorine  is  determined  volumetrically  by  Vol- 
hard's  method  and  the  chlorides  of  sodium  and  potassium  calculated  (see 
Stassfurt  Salts,  Determination  of  sodium  chloride).  A  better  method 
(especially  if  the  sodium  is  in  small  amount)  is  to  determine  the  potassium 
as  platinichloride  or  perchlorate  and  to  calculate  by  difference  the  sodium 
chloride,  which  is  then  expressed  as  carbonate  :  NaCl  X  0-906  =  Na2C03. 

Crude  potassium  carbonate  usually  contains  50-90%  of  K2CO3,  with  vary- 
ing proportions  of  water,  insoluble  substances,  sulphate,  chloride,  etc.  In  some 
crude  potashes  as  much  as  60%  of  sodium  carbonate  occurs,  but  the  best  qualities 
contain  about  2%. 

The  commercial  pure  carbonate,  from  Stassfurt  salts,  contains  96-98% 
K2CO3,  and  the  less  pure  forms  from  molasses  92%  K2CO3  with  more  or  less 
considerable  proportions  of  phosphate,  often  caustic  potash  and  sulphur  and 
cyanogen  compounds,  and  sodium  carbonate  (0-05-2-5%),  potassium  chloride 
(0-5-2-5%),  and  potassium  sulphate  (0-5-3%). 

The  chemically  pure  carbonate  may  still  contain  traces  of  chloride  and  sul- 
phate. 


POTASSIUM    CHLORATE 

KC1O3  =  122-56  (122-5) 

Colourless,  odourless  crystals  soluble  in  about  16  parts  of  cold  water ; 
when  heated  it  fuses  and  evolves  oxygen.  It  is  usually  met  with  in  the 
pure  state,  but  it  may  contain  small  quantities  of  chlorides,  hypochlorites, 
sulphates,  arsenic,  lead,  iron  and  lime.  Adulterations  with  nitre,  potassium 
chloride,  boric  acid  and  mica  have  been  detected.  These  impurities  may 
be  discovered  by  the  following  tests  and  the  chlorate  determined  as  in  7. 

1.  Chlorides,   Sulphates. — The  1:20  solution  is  tested  with  silver 
nitrate  or  barium  chloride. 

2.  Hypochlorites. — The  i  :  20  solution  should  give  no  immediate  blue 
coloration  with  potassium  iodide  and  starch  paste  in  the  cold,  but  the  pure 
chlorate  yields  a  faint  blue  after  some  minutes. 

3.  Nitrates. — i  gram,  heated  with  5  c.c.  of  sodium  hydroxide  solution, 
0-5  grams  of  iron  turnings  and  0-5  gram  of  zinc  dust,  should  not  evolve 
ammonia. 

4.  Metals,    Alkaline   Earths. — The   i  :  20   solution   is   treated  with 
hydrogen  sulphide  or  ammonia  and  ammonium  sulphide  or  ammonium 
oxalate  :    no  turbidity  should  appear. 

5.  Arsenic. — i  gram  is  strongly  heated  to  transform  it  into  chloride 
and  then  tested  in  the  Marsh  apparatus  (see  Flesh  Foods,  Vol.  II). 

6.  Boric  Acid,  Mica. — The  sample  is  treated  with  96%  alcohol  and 
filtered,  the  filtrate  being  tested  for  boric  acid  by  burning  the  alcohol  (green 


POTASSIUM  CYANIDE  83 

flame)  and  by  means  of  litmus  paper  (red  coloration).    The  mica  is  recog- 
nised by  its  insolubility  in  water. 

7.  Quantitative  Determination. — 0-1-0-2  gram  is  distilled  with 
hydrochloric  acid  and  the  chlorine  absorbed  in  potassium  iodide,  the  liberated 
iodine  being  titrated  with  thiosulphate  solution  :  i  c.c.  N/io-thiosulphate 
=  0-0020416  gram  KC103. 


POTASSIUM    CHLORIDE 

See  Stassfurt  Salts,  under  Fertilisers 

POTASSIUM    GHROMATE 

K2Cr04  =  194-2 

Yellow  crystals,  soluble  in  water.  It  is  moderately  pure  as  sold,  the 
most  frequent  impurities  being  free  alkalies  and  sulphates,  detectable  as 
follows  : 

1.  Free  Alkali. — The  aqueous  solution,  suitably  diluted,  is  tested  with 
a  few  drops  of  phenolphthalein. 

2.  Sulphates. — 3-5  grams  in  100  c.c.  of  water,  acidified  with  hydro- 
chloric acid,  are  tested  with  barium  chloride  :    with  the  pure  salt,  no  tur- 
bidity should  be  formed  even  after  12  hours. 

3.  Chlorides. — The  dilute  solution,  heated  with  nitric  acid  and  silver 
nitrate,  should  give  no  precipitate. 

4.  Alumina,   Alkaline   Earths. — The  I  :  20  solution  is  tested  with 
ammonia  and  ammonium  oxalate. 

5.  Quantitative  Determination. — See  Potassium  Dichromate, 

POTASSIUM    CYANIDE 

KCN  =  65-11  (65) 

White  or  dirty  white  powder  or  fused  masses,  very  readily  soluble  in 
water  to  an  alkaline  solution  and  soluble  also  in  alcohol  if  this  is  not  too 
concentrated.  The  usual  impurities  are  carbonates,  sulphates,  chlorides, 
sulphides,  cyanates,  thiocyanates,  ferrocyanides  and  soda.  Sometimes  it 
may  also  contain  small  quantities  of  heavy  metals,  especially  iron  and  lead, 
and  traces  of  silver.  The  tests  made  are  as  follows  : 

1.  Solubility. — i  gram  in  10  c.c.  of  water  should  give  a  clear  solution, 
and  2  grams  should  dissolve  at  the  ordinary  temperature  in  50  c.c.  of  70% 
alcohol  (by  weight). 

2.  Carbonates. — The  aqueous  solution   (i  :  10)  is  treated  with  lime 
water,  which  gives  a  white  turbidity  or  precipitate  in  presence  of  carbonates. 

3.  Sulphates. — -The  i  :  10  solution,  acidified  with  hydrochloric  acid 
(under  a  hood],  is  tested  with  barium  chloride. 

4.  Sulphides. — The  i  :  10  solution  is  tested  with  lead  acetate  :    black 
coloration  or  precipitate  in  presence  of  sulphide. 


84  POTASSIUM  BICHROMATE 

5.  Cyanates. — The  salt  is  triturated  with  about  84%  alcohol,  filtered 
and  concentrated,  and  hydrochloric  acid  added  :    if  cyanate  were  present, 
effervescence  wiU  occur. 

6.  Thiocyanates,  Ferrocyanides. — The  i  :  10  solution  is  tested  with 
a  few  drops  of  ferric  chloride,  which  gives  a  red  coloration  with  thiocyanates 
and  a  blue  precipitate  with  ferrocyanides. 

7.  Chlorides. — i  gram  is  mixed  with  2  grams  of  nitre  and  10  grams 
of  pure  potassium  carbonate  and  fused  to  decompose  the  cyanide,  the  fused 
mass  being  dissolved  in  water,  acidified  with  nitric  acid  and  tested  with 
silver  nitrate. 

8.  Soda. — i  gram  is  evaporated  to  dryness  with  excess  of  hydrochloric 
acid  (in  a  good  draught),  the  residue  being  dissolved  in  a  little  water  and 
tested  for  sodium  by  the  flame  or  by  means  of  potassium  pyroantimoniate. 

9.  Heavy   Metals. — The   i  :  10  solution  is  boiled  with  hydrochloric 
acid  until  all  the  hydrocyanic  acid  is  expelled  (in  a  good  draught]  and  then 
tested  with  hydrogen  sulphide,  with  subsequent  addition  of  ammonia. 

10.  Quantitative  Determination. — 10  grams  are  dissolved  in  water 
and  the  solution  made  up  to  a  litre  ;  to  25  c.c.  of  the  solution  (=  0-25  gram 
of  substance)  are  added  a  crystal  of  sodium  chloride  and  N/io-silver  nitrate 
then  run  in  from  a  burette  until  a  persistent  turbidity  is  obtained.     The 
number  of  c.c.  used,  multiplied  by  5-2,  gives  the  percentage  of  KCN  in  the 
sample.  * 

Chemically  pure  potassium  cyanide  contains  about  99%  KCN  ;  the  com- 
mercial pure  product  and  that  for  technical  purposes  contain  considerably  less 
(only  up  to  50%).  The  commercial  salt  often  contains  marked  proportions  of 
sodium  cyanide  and  when  this  is  calculated  as  potassium  cyanide,  the  content 
of  the  latter  appears  greater  than  the  true  value  (sometimes  even  greater  than 
100%)  ;  in  such  cases  the  soda  may  be  determined,  proceeding  as  in  8  (above) 
and  then  testing  the  alkali  chlorides  by  the  ordinary  methods  (see  Fertilisers, 
Stassfurt  Salts). 

POTASSIUM    BICHROMATE 

K2Cr207  =  294-2 

Orange  red  crystals  soluble  in  water.  The  commercial  salt  is  usually 
pure  or  almost  so,  only  containing  small  quantities  of  sulphates  and  of 
residue  insoluble  in  water.  It  may,  however,  contain  also  chlorides,  lime 
and  magnesia  and  may  be  adulterated  with  sodium  dichromate  (especially 
when  powdered).  Its  value  depends  essentially  on  the  content  of  real 
dichromate  or  of  chromic  anhydride.  The  analysis  includes,  therefore, 
the  following  tests  and  determinations  : 

1.  Sulphates. — 3  grams,  dissolved  in  100  c.c.  of  water,  acidified   with 

1  When  silver  nitrate  acts  on  potassium  cyanide,  it  gives  first  the  soluble  double 
cyanide  of  potassium  and  silver : 

AgNO3  +  2KCN  =  KAg(CN)2  +  KNO3  ; 

as  soon,  however,  as  the  silver  nitrate  is  in  excess,  it  reacts  with  the  sodium  chloride 
forming  insoluble  silver  chloride. 

If  the  sample  contains  appreciable  proportions  of  sulphides,  titration  with  silver 
nitrate  is  preceded  by  agitation  of  the  solution  with  powdered  lead  carbonate  and 
filtration. 


POTASSIUM  FERRICYANIDE  85 

30  c.c.  of  hydrochloric  acid  (D  1-12)  and  treated  in  the  hot  with  barium 
chloride,  should  give  no  turbidity  or  precipitate,  even  after  standing. 

2.  Chlorides. — I  gram  dissolved  in  water  and  acidified  with  nitric 
acid,  should  not  be  rendered  turbid  by  silver  nitrate. 

3.  Lime,  Magnesia. — 2  grams  dissolved  in  30  c.c.  of  water  and  mixed 
with  10  c.c.  of  ammonia  (D  =  0-96)  should  be  rendered  turbid  neither  by 
ammonium  oxalate  nor  by  sodium  phosphate. 

4.  Sodium  Salts. — These  are  detected  by  the  flame,  after  moistening 
with  hydrochloric  acid.     Indirectly  they  are  indicated  by  the  content  of 
chromic  anhydride  (see  5). 

5.  Determination  of  the  Dichromate. — This  can  be  carried  out  in 
two  ways  : 

(a)  BY  REDUCTION.  5  grams  of  the  dichromate  are  dissolved  in  water 
and  the  volume  made  up  to  I  litre.  10  c.c.  of  this  solution  (=  0-05  gram 
of  substance)  are  acidified  with  sulphuric  acid,  mixed  with  about  i  gram 
(weighed  exactly)  of  ferrous  ammonium  sulphate,  the  excess  of  the  ferrous 
salt  remaining  unaltered  being  then  titrated  with  N/io-permanganate. 
The  difference  between  the  quantity  of  iron  used,  which  is  given  by  (grams 
of  ferrous  ammonium  sulphate)  -f-  7,  and  that  of  the  iron  remaining  un- 
changed (i  c.c.  N/io-permanganate  =  0-0056  gram  Fe)  gives  the  amount 
of  iron  required  to  reduce  the  0-05  gram  of  substance  taken  :  Fe  X  0-8781  = 
K2Cr207  and  Fe  x  0-5969  =  CrO3. 

(6)  I  GEOMETRICALLY.  5  grams  of  dichromate  are  dissolved  to  i  litre. 
To  25  c.c.  of  the  solution  (0-125  gram  of  substance)  are  added  4-5  grams 
of  potassium  iodide,  20  c.c.  of  50%  sulphuric  acid  and  about  half  a  litre 
of  water,  the  iodine  liberated  being  titrated  with  N/io-sodium  thiosulphate 
in  presence  of  starch  paste,  i  c.c.  N/io-thiosulphate  =  0-0049  gram  of 
K2Cr2O7  or  0-00333  gram  of  CrO3. 

When  the  proportion  of  CrO3  found  is  greater  than  the  theoretical  pro- 
portion for  pure  potassium  dichromate  (68%),  the  presence  of  sodium 
dichromate  is  to  be  inferred. 

Commercial  potassium  dichromate  is  usually  guaranteed  to  contain  67-5- 
68%  of  CrO3. 


POTASSIUM    FERRICYANIDE  (Red  Prussiate  of  Potash) 

K,Fe2(CN)12  =  658-6 

Reddish-brown,  anhydrous  crystals  soluble  in  water,  insoluble  in  alcohol. 
It  may  contain  the  same  impurities  as  the  ferrocyanide,  these  being  detect- 
able similarly  (see  succeeding  article).  It  may  also  contain  ferrocyanide, 
detectable  as  follows  : 

1.  Ferrocyanide. — The  i  :  20  solution  is  treated  with  a  few  drops  of 
dilute  ferric  chloride  :  if  the  red  prussiate  is  pure  only  a  faint  brown  colora- 
tion appears,  whereas  in  presence  of  ferrocyanide  a  blue  coloration  or 
precipitate  is  formed. 

2.  Quantitative  Determination. — The  ferricyanide  is  first  reduced 
to  ferrocyanide  and  this  then  estimated.     2  grams  of  the  salt  are  dissolved 


86  POTASSIUM  HYDROXIDE 

in  100  c.c.  of  water  and  treated  with  an  excess  of  caustic  potash  and  then, 
drop  by  drop  and  with  shaking,  with  ferrous  sulphate  solution  until  a  black 
precipitate  appears  ;  the  volume  is  then  made  up  to  500  c.c.,  the  liquid 
filtered  and  the  ferrocyanide  in  25  c.c.  of  the  filtrate  (—  o-i  gram  of  sub- 
stance) determined  as  indicated  under  Potassium  Ferrocyanide  (5).  From 
the  quantity  and  titre  of  the  permanganate  used  the  ferricyanide  is  calcu- 
lated :  Fe  X  11769  =  K,Fe2(CN)12. 

If  the  red  prussiate  contains  ferrocyanide,  the  latter  is  determined 
directly  prior  to  reduction  and  allowance  then  made  for  it  in  the  above 
calculation. 


POTASSIUM  FERROCYANIDE  (Yellow  Prussiate  of  Potash) 

K4Fe(CN)6  +  3H20=  422-4 

Lemon-yellow  crystals  soluble  in  water.  The  usual  impurities  may 
contain  small  quantities  of  carbonates,  sulphates,  chlorides  and  soda.  The 
tests  are  as  follows  : 

1.  Carbonates. — The  powdered  salt  is  moistened  with  dilute  hydro- 
chloric acid  to  see  if  effervescence  occurs. 

2.  Sulphates. — The  i  :  20  solution,  acidified  with  hydrochloric  acid, 
is  tested  with  barium  chloride. 

3.  Chlorides. — I  gram  is  fused  with  2  grams  of  nitre  in  a  porcelain 
crucible  and  the  mass  dissolved  in  water,  acidified  with  nitric  acid  and 
tested  with  silver  nitrate. 

4.  Soda. — The  solution  of  1-2  grams  in  100  c.c.  of  water  is  acidified 
with  a  little  hydrochloric  acid  and  treated  with  a  slight  excess  of  ferric 
chloride,  the  liquid  being  filtered  and  the  excess  of  iron  in  the  filtrate  pre- 
cipitated with  ammonia.    The  solution  is  again  filtered,  the  filtrate  being 
concentrated  to  small  volume  and  tested  for  sodium  by  means  of  potassium 
pyroantimoniate. 

5.  Quantitative  Determination. — 10  grams  are  dissolved  in  water 
to  i  litre,  10  c.c.  (=  o-i  gram  of  substance)  being  diluted  in  a  porcelain 
dish  with  about  250  c.c.  of  water,  acidified  with  dilute  sulphuric  acid  and 
titrated  with  permanganate.     The  ferrocyanide  is  then  calculated  from  the 
titre  of  the  permanganate  :    Fe  X  7-56  =  K4Fe(CN)6,  3H20. 

Commercial  yellow  prussiate  is  usually  moderately  pure,  containing  at  least 
99%  of  K4Fe(CN)6)3H20. 


POTASSIUM    HYDROXIDE  (Caustic  Potash) 

KOH  =  56-1  (56) 

This  is  sold  in  lumps,  scales,  sticks  (ingots)  or  powder,  or  in  solution 
and  in  various  degrees  of  purity,  such  as  Caustic  potash  -puriss.  or  by  baryta, 
prepared  from  the  sulphate  and  from  baryta,  Caustic  potash  pure  by  alcohol, 
Caustic  potash  pure  by  lime,  and  Ctude  caustic  potash.  The  impurities  it 
contains  vary  in  nature  (especially  carbonates,  sulphates,  chlorides,  nitrates, 


POTASSIUM  HYDROXIDE  87 

silica,  alumina  and  ferric  oxide)  and  in  proportions.     The  tests  made  are 
as  follows  : 

1.  Solubility. — 10  grams  with  20  c.c.  of  water  should  give  a  clear, 
colourless  solution.     Any  insoluble  residue  (silica,  ferric  oxide,  etc.)  may 
be  filtered  off  and  weighed. 

5  grams  dissolved  in  10  c.c.  of  water  and  treated  with  25  c.c.  of  95% 
alcohol,  should  give  a  clear,  homogeneous  solution,  which  does  not  separate 
into  two  layers  on  standing  (carbonates  and  other  salts). 

2.  Chlorides. — 2  grams  are  dissolved  in  water,  acidified  with  nitric 
acid  and  made  up  to  60  c.c.  ;  silver  nitrate  should  then  cause  only  a  faint 
opalescence. 

3.  Sulphates. — 3  grams  are  dissolved  in  50  c.c.  of  water,  acidified  with 
hydrochloric  acid,  boiled  and  treated  with  barium  chloride.     Any  turbidity 
or  precipitate  formed  after  an  hour  is  observed. 

4.  Nitrates. — 2  grams  are  dissolved  in  water,  neutralised  with  sulphuric 
acid  and  diluted  to  25  c.c.,  this  solution  being  poured  carefully  into  a  test- 
tube  containing  10  c.c.  of  cone,  sulphuric  acid  with  a  few  crystals  of  diphenyl- 
amine  :  any  blue  coloration  foimed  at  the  zone  of  contact  of  the  two  liquids 
within  a  few  minutes  is  noted. 

5.  Carbonates. — 2  grams  are  dissolved  in  10  c.c.  of  water  and  the 
solution  poured  into   dilute    (i  :  i)   hydrochloric  acid,  any  effervescence 
being  observed. 

6.  Phosphates. — 5  grams,  dissolved  in  water  and  acidified  with  nitric 
acid,  are  treated  with  ammonium  molybdate  and  gently  warmed  :    the 
formation  of  a  yellow  precipitate  within  about  two  hours  is  noted. 

7.  Silica. — 5  grams  are  dissolved  in  dilute  hydrochloric  acid,  the  liquid 
evaporated  to  dryness,  the  residue  heated  at  105°,  and  taken  up  in  water 
again  :    gelatinous  flocks  separate  after  some  time  if  silica  is  present. 

8.  Alumina. — 5  grams  are  dissolved  in  dilute  acetic  acid,  a  slight  excess 
of  ammonia  being  added  and  the  volume  made  up  to  100  c.c.  with  water  : 
the  deposition  of  gelatinous  flocks  immediately  or  within  about  two  hours 
indicates  alumina. 

9.  Heavy  Metals. — 5  grams,  dissolved  in  slight  excess  of  dilute  hydro- 
chloric acid,  are  treated  with  hydrogen  sulphide  and  any  turbidity  noted, 
either  before  or  after  addition  of  excess  of  ammonia. 

10.  Sodium. — The  solution  in  hydrochloric  acid  is  tested  in  the  Bunsen 
flame. 

11.  Ammonia. — 2-3  grams  are  dissolved  in  water  and  the  solution 
tested  with  2-3  drops  of  Nessler  solution. 

12.  Quantitative    Determination. — The    total    alkalinity    and    the 
alkalinity  after  treatment  with  barium  chloride  are  determined  with  methyl 
orange  as  indicator,  the  amounts  of  potassium  hydroxide  and  carbonate 
being  thus  obtained,   i  c.c.  N-acid  =  0-056  gram  KOH  or  0-069  gram  K2CO3. 

The  determination  of  the  various  impurities  is  carried  out  by  methods 
similar  to  those  indicated  under  "  Sodium  Carbonate  "  (q.v.). 


* 
*  * 


The  best  potassium  hydroxide  is  that  termed  "  by  baryta  "  ;   then  come  that 
"  by  alcohol  "  and  that  "by  lime." 


88  POTASSIUM  LACTATE 

Caustic  potash  by  baryta  should  contain  only  traces  of  chlorides  (faint  opales- 
cence  with  silver  nitrate)  and  should  not  give  the  reactions  for  sulphates, 
nitrates,  carbonates,  etc.  (vide  supra).  Its  content  in  KOH  should  not  be  less 
than  80%,  the  remainder  being  water,  which  is  inevitable  in  the  purest  products. 

In  potassium  hydroxide  by  alcohol  traces  of  chlorides,  sulphates,  silica  (separa- 
tion of  flocks  in  test  7)  and  alumina  (few  flocks  after  some  hours  in  test  8)  are 
allowable  ;  the  water  should  not  exceed  20%. 

In  potassium  hydroxide  by  lime  small  proportions  of  the  above  impurities, 
such  as  chlorides,  sulphates,  etc.,  are  tolerated.  Its  total  alkalinity  should  be 
not  less  than  80%  and  its  content  of  carbonate  not  more  than  5%. 

Crude  caustic  potash  contains  marked  amounts  of  chlorides,  sulphides,  car- 
bonates, etc.  ;  its  value  depends  essentially  on  the  proportion  of  KOH,  deter- 
mined as  in  12. 


POTASSIUM    IODIDE 

KI  =  166-12 

White  (or  faintly  yellow  if  very  old)  crystals,  extremely  soluble  in 
water.  It  may  contain  bromides,  chlorides,  iodates,  cyanides  and  the  other 
impurities  found  in  the  bromide.  The  principal  impurities  are  tested  for 
as  follows  : 

1.  Iodates,   Carbonates. — The  powdered  substance  is  treated  with 
dilute  sulphuric  acid  ;  effervescence  indicates  carbonates,  and  yellow  colora- 
tion, iodates.     To  5  c.c.  of  the  I  :  20  solution  are  added  a  few  drops  of 
starch  paste  and  5-6  drops  of  dilute  tartaric  acid  (i  :  50)  ;   in  presence  of 
iodates,  the  liquid  turns  blue. 

2.  Chlorides,  Bromides. — About  0*5  gram  is  dissolved  in  ammonia, 
treated  with  silver  nitrate,  shaken,  filtered,  and  the  filtrate  acidified  with 
nitric  acid  :    with  chloride  or  bromide,  a  precipitate  forms. 

3.  Cyanides. — The  solution  (i  :  20),  treated  with  a  crystal  of  ferrous 
sulphate,  a  drop  of  ferric  chloride,  eight  drops  of  sodium  hydroxide  solution 
and,  after  gentle  heating,  acidified  with  hydrochloric  acid,  becomes  blue 
if  cyanides  are  present. 

4.  Sulphates,  Metals,  Alkaline  Earths. — -See  Potassium  Bromide  (i). 

Pure  potassium  iodide  for  pharmaceutical  purposes  should  contain,  accord- 
ing to  the  Italian  Pharmacopoeia,  neither  iodates,  carbonates,  sulphates,  heavy 
metals,  nor  cyanides.  Test  2  (above)  should  give  at  most  a  faint  white  or 
yellowish  opalescence. 

POTASSIUM    LACTATE 

For  use  in  dyeing,  an  acid  lactate  of  potassium,  KH5C3O3  +  H6C303, 
is  sold  under  the  name  Lactolin  as  a  yellowish-brown,  syrupy  liquid,  con- 
taining about  50%  by  weight  of  the  acid  lactate.  Lactolin  A  and  Lactolin 
B  represent  the  corresponding  acid  lactates  of  sodium  and  ammonium. 

The  impurities  of  these  products  are  the  same  as  in  lactic  acid  and  are 
investigated  in  the  same  way  (see  Lactic  Acid). 

The  free  acid  is  determined  by  titration  with  N-alkali  in  presence  of 
phenolphthalein  and  the  total  acid  by  oxidation  with  permanganate,  accord- 
ing to  Ulzer  and  Seidel  (see  Lactic  Acid). 


POTASSIUM  NITRATE  89 

POTASSIUM    NITRATE 

KN03  =  ioi-i 

Large,  colourless,  rhombic  prisms  or  dry,  white  crystalline  powder, 
soluble  in  4  parts  of  cold  water,  insoluble  in  absolute  alcohol.  Crude  nitre 
may  contain  various  impurities  (up  to  20%),  namely,  chlorides,  chlorates, 
perchlorates,  sulphates,  nitrites,  iodates,  lime,  magnesia,  soda,  copper, 
and  insoluble  substances  (sand,  earthy  matter).  In  general  refined  nitre 
is  fairly  pure,  only  containing  traces  of  chlorides.  The  tests  to  be  made 
are  as  follows  : 

1.  Insoluble  Substances,  Metals,  Alkaline  Earths,  etc. — 5  grams 
are  dissolved  in  50  c.c.  of  water,  filtered  from  any  insoluble    residue    and 
the  filtrate  tested  with  ammonia,  ammonium  sulphide,  ammonium  oxalate 
and  sodium  phosphate  (see  also  Potassium  Hydroxide). 

2.  Sodium  Salts. — If  the  nitre  does  not  colour  the  flame  yellow  it  is 
free  from  sodium  salts,  while  if  it  does  give  a  colour  these  salts  may  be 
present  only  in  traces.     The  nitre  is  well  and  repeatedly  triturated  with 
alcohol  and  the  liquid  filtered  and  evaporated  :    in  presence  of  sodium 
nitrate,  the  residue  is  composed  almost  exclusively  of  this  salt. 

3.  Chlorides,  Sulphates. — The  solution  (i  :  20)  is  tested  with  silver 
nitrate  and  with  barium  chloride  :   with  pure  nitre,  no  turbidity  should  be 
observed  even  after  some  hours. 

4.  Chlorates,  Perchlorates. — Where  no  chlorides  are  present,  chlorates 
or  perchlorates  may  be  detected  by  calcining  a  little  of  the  nitre,  dissolving 
the  residue  in  water  acidified  with  nitric  acid  and  testing  with  silver  nitrate  : 
a  turbidity  indicates  chlorate  or  perchlorate.     If  this  test  gives  an  affirmative 
result,  and  also  if  the  nitre  contains  chlorides,  the  chlorates  and  perchlorates 
may  be  determined  as  follows  : 

(a)  5  grams  of  the  nitre  are  dissolved  in  water,  filtered  if  necessary, 
then  slightly  acidified  with  nitric  acid  and  the  liquid  titrated  with  silver 
nitrate  and  decinormal  thiocyanate  according  to  Volhard's  method.     The 
chlorine  thus  found  exists  as  chlorides. 

(b)  5  grams  of  the  nitre  and  10  grams  of  zinc  dust  (free  from  chlorine) 
are  gently  boiled  for  half  an  hour  with  150  c.c.  of  i%  acetic  acid,  the  liquid 
being  filtered  and  the  chlorine  in  the  filtrate  determined.     This  chlorine  is 
that  of  the  chlorides  and  chlorates. 

(c)  In  a  flat  platinum  dish,  5  grams  of  the  nitre  are  mixed  to  a  paste 
with  about  i  c.c.  of  pure,  saturated  sodium  carbonate  solution  by  means 
of  a  platinum  wire  ;   the  paste  is  then  dried  over  a  small  flame  and  heated 
gradually  to  redness.     When  cool,  the  mass  is  taken  up  with  water,  the 
solution  being  acidified  with  nitric  acid  and  the  chlorine  again  determined  : 
this  represents  the  chlorine  of  the  chlorides,  chlorates  and  perchlorates. 

5.  Iodates. — A  solution  of  5  grams  of  the  nitre  is  acidified  with  dilute 
sulphuric  acid  and  zinc  turnings  and  a  little  starch  paste  added  :   presence 
of  iodates  is  indicated  by  a  blue  coloration. 

6.  Nitrites. — To  the  i  :  10  solution  of  the  nitre  are  added  6  drops  of 
I  :  50  sulphuric  acid,  a  little  starch  paste  and  3-4  drops  of  potassium  iodide 


90  POTASSIUM  PERMANGANATE 

solution  (i  :  20)  free  from  iodates  :  in  presence  of  nitrites,  a  blue  coloration 
is  obtained  almost  immediately.1 

7.  Quantitative  Determination. — Analogous  to  that  of  sodium  nitrate 
(see  Fertilisers). 

Nitre  for  the  manufacture  of  gunpowder  should  not,  according  to  French 
requirements,  contain  more  than  0-033%  °f  sodium  chloride  ;  according  to  the 
German,  not  more  than  0-010%,  and  according  to  the  English  and  Italian,  not 
more  than  0-005%.  Further,  it  should  contain  only  traces  of  chlorates  and 
perchlorates. 

POTASSIUM    OXALATE 

Various  potassium  oxalates  exist  :  Neutral  oxalate,  K2C204  +  H20  = 
184-2,  colourless  crystals,  soluble  in  3  parts  of  cold  water  to  a  neutral  solu- 
tion. The  Acid  oxalate  or  bioxalate,  KHC204  +  H2O  —  146-1,  in  colourless, 
transparent,  rhomboidal  crystals,  soluble  in  25  parts  of  cold  water  to  an 
acid  solution.  The  Quadr oxalate  or  Tetr oxalate,  KHC2O4,  H8C2O4  +  2H2O 
=  254-1,  colourless  crystals  soluble  in  about  55  parts  of  cold  water  to  an 
acid  solution.  Salts  of  Sorrel,  a  mixture  of  the  bi-  and  tetr-oxalate,  soluble 
in  40  parts  of  water  giving  an  acid  solution.  In  these  products  the  impurities 
to  be  tested  for  are  chlorides,  sulphates  and  lead  : 

1.  Chlorides,   Sulphates. — The  solution,   acidified  with  nitric  acid, 
is  tested  with  silver  nitrate  or  barium  chloride. 

2.  Lead  and  other  Heavy  Metals. — i  gram,  dissolved  in  water  and 
rendered  alkaline  with  ammonia,  is  treated  with  ammonium  sulphide, 

3.  Determination  of  the  Oxalic  Acid. — The  total  acid  is  determined, 
either  by  precipitating  as  calcium  oxalate  with  ammonia  and  calcium  chloride, 
and  weighing  as  lime  (i  part  CaO  =  1-607  part  H2C2O4),  or  volumetrically 
with  permanganate  (i  c.c.  N/io-permanganate  =0-0045  gram  H2C2O4). 

The  free  acid,  derived  from  the  bioxalate  or  tetroxalate  and  used  to 
deduce  the  nature  of  the  acid  salt,  is  determined  by  titration  with  N-alkali 
in  presence  of  phenolphthalein  :  i  c.c.  N-alkali  =  0-045  gram  H2C204. 

i  gram  KHC2O4  +  H2O  requires  6-85  c.c.  N-alkali. 

I  gram  KHC2O4,  H2C204  +  2H2O  requires  11-80  c.c.  N-alkali. 

POTASSIUM    PERMANGANATE 

KMnO4  =  158 

Violet-red  crystals  of  metallic  lustre,  soluble  in  16  paits  of  cold  water. 
The  tests  made  are  as  follows  : 

1.  Chlorides,  Sulphates. — 2  grams  are  dissolved  in  50  c.c.  of  water 
and  the  solution  heated  with  10  c.c.  of  alcohol  until  decolorisation  is  com- 
plete.    The  liquid  is  filtered  and  the  filtrate  acidified  with  nitric  acid  and 
tested  with  silver  nitrate  and  with  barium  chloride. 

2.  Nitrates. — i  gram  is  dissolved  in  10  c.c.  of  water  and  the  solution, 
after  decolorisation  with  oxalic  acid,  mixed  with  an  equal  volume  of  cone. 

1  If  the  potassium  iodide  is  not  absolutely  free  from  iodates,  the  blue  coloration 
may  also  appear,  at  any  rate  after  some  time.  The  test  is,  of  course,  invalid  if  the 
nitre  contains  iodates. 


POTASSIUM   SULPHIDE  91 

sulphuric  acid  ;  when  ferrous  sulphate  solution  is  poured  carefully  on  to 
the  surface  of  the  liquid,  no  brown  coloration  should  be  formed  at  the  zone 
of  contact. 

3.  Quantitative  Determination. — The  solution  is  titrated  with 
ferrous  ammonium  sulphate  or  N/io-oxalic  acid.  To  10  c.c.  of  N/io- 
oxalic  acid,  mixed  with  I  c.c.  of  dilute  sulphuric  acid  (i  :  4),  the  perman- 
ganate solution  (3-16  grams  per  litre)  is  run  in  until  a  persistent  pink  colora- 
tion appears  ;  with  the  pure  salt,  10  c.c.  should  be  required. 


POTASSIUM    PERSULPHATE 

(See  under  Ammonium  Persulphate) 

POTASSIUM    SULPHATE 

K£0t  =  174 

The  crude  sulphate  for  fertilising  purposes  (see  Potassium  Salts,  under 
Fertilisers)  and  the  pure  sulphate,  in  large,  colourless  crystals  soluble  in 
water,  are  on  the  market.  The  latter  may  contain  small  quantities  of 
chlorides,  calcium,  magnesium  and  sodium  salts,  and  potassium  hydrogen 
sulphate.  These  impurities  are  detected  as  follows  : 

1.  Chlorides. — The  solution,  acidified  with  nitric  acid,  should  give 
no  turbidity  with  silver  nitrate. 

2.  Metals. — The  solution  should  not  change  with  ammonium  sulphide, 
ammonia,  ammonium  oxalate  or  sodium  phosphate. 

3.  Sodium  Salts. — These  are  recognised  by  the  yellow  coloration  of 
the  flame. 

4.  Bisulphate. — When  bisulphate  is  present,  the  reaction  is  acid  to 
litmus  paper. 

POTASSIUM    SULPHIDE 

K2S  +  5H2O  =  200-2 

The  ordinary  sulphide  forms  colourless,  greenish  or  yellowish,  deliquescent 
crystals  or  fused,  yellowish-red  hygroscopic  masses  (K2S),and  is  not  much 
used.  More  common  is  a  mixture  of  Potassium  polysulphides  with  thio- 
sulphate  and  sulphate,  known  as  Liver  of  sulphur,  which  forms  deliquescent, 
greenish-yellow  masses,  reddish-brown  inside,  with  a  sulphurous  odour, 
largely  soluble  in  water  and  partly  so  in  alcohol  (about  50%). 

The  analysis  is  carried  out  as  with  the  corresponding  sodium  salt  (q.v.}  ; 
i  c.c.  N/io-zinc  sulphate  =  0-05  gram  K2S  +  5H2O  =  0-02755  gram  K2S. 

For  the  analysis  of  liver  of  sulphur  it  is  usually  sufficient  to  verify  the 
external  characters  (the  fracture  should  exhibit  a  reddish-brown  liver  colour) 
and  the  reactions  for  polysulphides  and  potassium  (with  excess  of  hydro- 
chloric acid,  hydrogen  sulphide  should  be  evolved  and  sulphur  deposited  ; 
if  the  liquid  is  then  boiled  and  filtered  and  the  filtrate  evaporated  to  dryness, 


92  SODIUM  ALUMINATE 

the  residue  should  give  the  reactions  for  potassium  in  the  flame  and  with 
tartaric  acid). 

SILVER    NITRATE 

AgN03  =  169-94  (170) 

Transparent,  colourless  crystals,  alterable  in  the  light  in  presence  of 
organic  matter,  soluble  in  0-5  part  of  water,  in  alcohol  o»  in  ether.  The 
tests  to  be  made  are  : 

1.  Solubility. — i  part,  with  0-5  part  of  water,  should  give  a  solution 
which  is  clear  and  remains  so  after  addition  of  alcohol. 

2.  Extraneous  Salts. — i  gram,  dissolved  in  40  c.c.  of  water,  is  treated 
with  6  c.c.  of  N-hydrochloric  acid  ;  the  silver  chloride  is  allowed  to  deposit 
in  the  hot  and  the  filtered  liquid  evaporated  and  the  residue  ignited  gently  : 
no  appreciable  residue  should  remain — merely  a  faint  black  stain  of  reduced 
silver. 

SODIUM    ACETATE 

NaC2H302  +  aH2O  =  136-12 

Colourless  crystals  extremely  soluble  in  water  and  in  25  parts  of  90% 
alcohol ;  also  the  anhydrous  salt  (Fused  sodium  acetate)  in  greyish,  fused 
masses.  The  pure  salt  should  answer  the  following  tests  : 

1.  Reaction.— The    i  :  10  solution   should   be   clear  and   should   not 
redden  phenolphthalein  and  should  react  slightly  alkaline  with  litmus  paper. 

2.  Empyreumatic  or  Tarry  Substances. — 0-5  gram  should  dissolve 
in  pure  cone,  sulphuric  acid  without  browning.     0-5  gram,  dissolved  in 
water,  acidified  with  5  c.c.  of  pure  dilute  sulphuric  acid  (i  :  3)  and  treated 
with  i  drop  of  N/io-permanganate,  should  have  a  persistent  pink  colour 

3.  Extraneous   Metals. — The   i  :  10  solution,   acidified  with  hydro- 
chloric acid,  should  not  give  a  blue  colour  with  potassium  ferrocyanide  (iron) 
and  should  not  change  with  hydrogen  sulphide  (heavy  metals)  ;   acidified 
with  acetic  acid,  it  should  undergo  no  change  with  ammonium  oxalate 
(lime)  ;   acidified  with  nitric  acid,  it  should  give  no  turbidity,  even  after 
standing,  with  barium  chloride  (sulphates),  and  with  silver  nitrate  should 
give  at  most  a  slight  opalescence  (chlorides). 

SODIUM    ALUMINATE 

Al2Na2O4  =  164-2 

This  is  sold  in  white  crystalline  masses,  or  as  a  moist  paste,  or  in  solution. 
It  is  soluble  in  water  but  the  solution  becomes  cloudy  in  the  air.  The 
common  impurities  are  insoluble  substances,  silica  and  iron  (see  1-3,  below), 
and  the  value  depends  on  the  content  of  alumina  and  sodium  oxide  (see  4). 

1.  Insoluble  Substances. — 10-20  grams  are  dissolved  in  hot  water 
and  the  solution  filtered  through  a  tared  filter,3  the  insoluble  part  being 

1  As  it  is  an  alkaline  liquid  it  is  best  to  use  a  filter  of  either  hardened  paper  or  other 
similar  good  filter-paper. 


SODIUM  BICARBONATE  93 

washed,  first  with  hot  water,  then  with  dilute  hydrochloric  acid  and  finally 
with  water  again  ,    it  is  then  dried  and  weighed. 

2.  Silica. — -5—10  grams  of  the  substance  are  dissolved  in  hydrochloric 
acid,  the  liquid  evaporated  to  dryness,  the  residue  heated  at  110-120°, 
taken  up  with  hydrochloric  acid,  filtered,  washed,  ignited  and  weighed. 

3.  Iron. — This  is  detected  and  determined  as  in  aluminium  sulphate 
(q.v.}. 

4.  Determination  of  the  Alumina  and  Soda. — Results  sufficiently 
accurate  for  technical  purposes  are  given  by  Lunge's  method  : 

20  grams  of  the  aluminate  are  dissolved  in  water  to  i  litre  and  10  c.c. 
of  this  solution  (=  0-2  gram  of  substance)  boiled  and  titrated  with  N/5- 
hydrochloric  acid  in  presence  of  phenolphthalein  until  the  latter  is  decolorised 
(only  the  alkali  of  the  aluminate  being  neutralised).  The  liquid  is  then 
cooled  to  30-37°,  a  drop  (not  more)  of  methyl  orange  added,  and  the  liquid 
then  retitrated  with  the  same  acid  to  an  incipient  red  tint  (the  aluminium 
hydroxide  liberated  in  the  preceding  reaction  is  then  neutralised).  From 
the  number  of  c.c.  of  acid  used  in  the  first  titration  (phenolphthalein)  the 
soda  is  calculated  (i  c.c.  N/5-HC1  =  0-00621  gram  Na2O)  and  from  the 
number  of  c.c.  used  in  the  second  titration  (methyl  orange)  the  alumina  is 
calculated  (i  c.c.  N/5-HC1  =  0-003407  gram  A12O3). 

For  more  exact  determinations  phenolphthalein  should  be  added  to  the 
aluminate  solution,  a  current  of  carbon  dioxide  being  then  passed  through 
it  until  the  red  colour  disappears.  The  precipitated  aluminium  hydroxide 
is  filtered  off,  washed,  dried,  ignited  and  weighed  as  A12O3.  In  the  filtrate 
the  Na  2O  is  determined  by  titration  with  N/5-hydrochloric  acid  in  presence 
of  methyl  orange. 

SODIUM    BICARBONATE 

NaHCO3  =  84-06  (84) 

Crystalline  crusts  or  white  powder  with  slightly  alkaline  taste,  soluble 
in  12  parts  of  water.  It  may  contain  the  same  impurities  as  the  normal 
carbonate  but  especially  ammonium  salts  (chloride),  thiosulphates,  arsenites 
and  normal  carbonate.  The  tests  to  be  made  are  : 

1.  Ammonia,    Chlorides. — i    gram   should   not   give   off    ammonia 
when  heated  in  a  test-tube,  and  when  dissolved  in  50  c.c.  of  water  and  treated 
with  a  few  drops  of  Nessler  solution  should  not  colour.     With  silver  nitrate 
in  presence  of  nitric  acid,  no  more  than  a  slight  opalescence  should  develop 
in  10  minutes. 

2.  Arsenites,  Thiosulphates. — A  solution  of  i  gram  in  50  c.c.  of 
water,  acidified  with  acetic  acid  and  treated  with  silver  nitrate,  should  not 
give  either  yellow  (ar senile)  or  brown  opalescence  (thiosulphate}. 

3.  Normal  Carbonate. — i  gram  dissolved  in  50  c.c.  of  cold  water 
without  too  much  shaking,  should  not  turn  red  on  addition  of  3  drops  of 
phenolphthalein  solution  (less  than  2%  of  normal  carbonate).     Quantitative 
determination  of  the  carbonate  and  bicarbonate  may  be  carried  out  thus  : 

5  grams  are  dissolved  in  about  100  c.c.  of  cold  boiled  water  without 
shaking  but  merely  crushing  with  a  glass  rod  ;  to  the  solution  about  10 


94  SODIUM  BISULPHITE 

grams  of  pure  sodium  chloride  are  then  added  and  the  whole  cooled  to  o° 
and  titrated  with  N-hydrochoric  acid  in  presence  of  phenolphthalein  until 
the  red  coloration  disappears  (i  c.c.  N-acid  =  0-053  gram  Na2CO3).  Methyl 
orange  is  next  added  and  the  titration  continued  with  the  same  acid  to  a 
red  colour  (i  c.c.  N-acid  =  0-084  gram  NaHC03). 


SODIUM  BISULPHATE 

NaHSO4+H2O=i38 

Colourless  crystals  or  white,  fused  masses,  soluble  in  water  to  an  acid 
solution.  It  may  contain  the  same  impurities  as  the  sulphate  and  these 
are  detected  by  similar  methods  (see  Sodium  Sulphate).  The  content  of 
pure  sodium  bisulphate  is  determined  thus  : 

Quantitative  Determination. — 4-5  grams  are  dissolved  in  water  and 
titrated  with  normal  alkali  (methyl  orange)  :  i  c.c.  N-alkali  =  0-120  gram 
NaHSO4  or  0-0138  gram  NaHS04  +  H20. 

SODIUM    BISULPHITE 

NaHS03  =  104-1  (104) 

This  is  put  on  the  market  in  crystals,  or  moist  crystalline  masses,  or  dry 
white  powder,  or  solution  ;  the  crystals  and  the  dry  powder  are  usually 
odourless,  but  the  other  qualities  smell  of  sulphur  dioxide.  It  is  soluble 
in  water  giving  an  acid  solution. 

It  may  contain  the  same  impurities  as  the  neutral  sulphite  and  these 
are  similarly  detected  (see  Sodium  Sulphite)  ;  iron  and  sulphate  especially 
should  be  tested  for.  Its  value  depends  essentially  on  the  content  of  bisul- 
phite or  sulphur  dioxide  (free  ;  semi-combined,  that  is,  as  bisulphite  ;  com- 
bined, that  is,  as  normal  sulphite),  which  is  determined  as  follows  : 

Quantitative  Determination. — -This  is  based  on  the  facts  that  the 
total  sulphur  dioxide  may  be  estimated  by  titration  with  iodine  and  that 
the  free  or  semi-free  sulphur  dioxide  reacts  acid  towards  phenolphthalein, 
whereas  the  semi-free  has  a  neutral  reaction  towards  methyl  orange.  In 
other  words  :  with  phenolphthalein  only  the  normal  sulphite  reacts  neutral, 
while  with  methyl  orange  the  bisulphite  also  reacts  neutral ;  free  sulphur 
dioxide  is  acid  towards  both  indicators. 

(a)  TOTAL  SULPHUR  DIOXIDE. — 5  grams  are  dissolved   to   i  litre  in 
recently  boiled  and  cooled  water,  this  solution  being  run  from  a  burette  into 
15  c.c.  N/io-iodine  solution  in  a  flask  until  the  liquid  is  almost  decolorised  ; 
starch  paste  is  then  added  and  the  titration  continued  until  the  blue  colour 
disappears  :    i  c.c.  N/io-iodine  =  0-0032  gram  SO2. 

(b)  FREE  AND  SEMI-FREE  SULPHUR  DIOXIDE.— 200  c.c.  of  the  solution 
prepared  as  in  (a)  are  titrated  with  N-sodium  hydroxide  in  presence  of 
methyl  orange  until  a  yellow  coloration  is  attained  ;    this  gives  the  free 
SO 2  (i  c.c.  N-alkali  =  0-064  gram  S02).     Phenolphthalein  is  then  added 
and  the  N-sodium  hydroxide  run  in  until  a  red  colour  appears  ;   this  gives 
the  semi-free  SO2  (i  c,c.  N-alkali  =  0-032  gram  SO2).     These  two  values 


SODIUM   CARBONATE  95 

together,  when  subtracted  from  the  total  sulphur  dioxide,  give  that  existing 
as  normal  sulphite. 

Commercial  solid  sodium  bisulphite,  sometimes  called  also  Metasulphite  or 
Pyrosulphite  (see  Potassium  bisulphite) ,  usually  contains  60-62%  of  total  SO2  ; 
the  solution  of  38-40°  Baume  contains  24-25%. 

SODIUM    CARBONATE 

Na2CO3  =  106  ;    Na2CO3  +  ioH2O  =  286 

This  is  sold  as  :  Crude  sodium  carbonate  (Crude  soda],  in  more  or  less 
coloured,  crystalline  masses,  contaminated  by  chlorides,  sulphates,  sulphides, 
thiocyanates,  phosphates,  silica,  heavy  and  earthy  metals  "and  sodium 
hydroxide ;  Crystallised  carbonate  (Soda  crystals]  with  10  mols.  of  water, 
containing  particularly  sulphates  and  chlorides  but  not  in  large  proportions  ; 
Dry  carbonate  (Calcined  soda  or  Soda  ash)  in  white  powder  or  masses,  which 
may  contain  sulphate,  sulphide  and  hydroxide  if  made  by  calculation  of 
Leblanc  soda,  or  chloride  and  bicarbonate,  if  it  is  Solvay  or  ammonia  soda. 
There  is  also  pure  sodium  carbonate  (crystallised  or  dry),  which  should  be 
free  from  impurities. 

The  analysis  of  sodium  carbonate  includes  the  qualitative  investigation 
of  the  various  impurities  (tests  1-14),  to  be  made  particularly  on  the  pure 
and  chemically  pure  products  ;  and  the  determination  of  the  water,  titre 
and  some  of  the  commoner  impurities,  especially  with  commercial  sodas 
(15-17).  The  quantities  given  for  tests  1-9  refer  to  the  crystallised  car- 
bonate ;  one-third  as  much  of  the  anhydrous  carbonate  should  be  taken. 

1.  Solubility. — i  gram  in  10  c.c.  of  water  should  give  a  clear  solution. 

2.  Sulphates,  Chlorides. — 5  grams,  dissolved  in  a  slight  excess  of 
dilute  nitric  acid  and  the  solution  made  up  to  25  c.c.  with  water,  are  tested 
with  barium  chloride  in  the  hot — examining  after  standing  for  12  hours 
(sulphates} — or  with  silver  nitrate  (chlorides}. 

3.  Nitrates. — See  Caustic  Potash. 

4.  Phosphates. — 20  grams  dissolved  in  dilute  nitric  acid  are  treated 
with  ammonium  molybdate  at  a  gentle  heat. 

5.  Silica. — 20  grams  are  dissolved  in  dilute  hydrochloric  acid  and 
evaporated  on  a  steam-bath,  the  residue  being  dried  at  105°  and  taken  up 
in  water  :  the  solution  thus  obtained  should  be  clear  and  should  not  deposit 
flocks  even  after  long  standing. 

6.  Arsenic. — The  solution  is  tested  in  the  Marsh  apparatus  for  one  hour. 

7.  Alumina. — 10  grams  dissolved  in  50  c.c.  of  water  are  acidified  with 
acetic  acid,  and  then  rendered  alkaline  with  ammonia  :   any  formation  of 
gelatinous  flocks  after  long  standing  is  noted. 

8.  Heavy  Metals. — 10  grams  are  dissolved  in  water  (50  c.c.),  acidified 
with  dilute  hydrochloric  acid  and  treated  with  hydrogen  sulphide  :    no 
change  should  occur  even  after  addition  of  ammonia  in  excess. 

9.  Potassium. — 3  grams,   dissolved  in  dilute  hydrochloric  acid,  are 
treated  with  a  few  drops  of  platinic  chloride  and  the  liquid  evaporated  on 
a  steam-bath  ;  the  dry  residue  should  give  a  clear  solution  in  50  c.c.  of  80% 
alcohol. 


96  SODIUM  CARBONATE 

10.  Ammonia. — See  Caustic  Potash. 

11.  Sodium  Hydroxide. — 3  grams,  dissolved  in  50  c.c.  of  water,  are 
treated  with  6  grams  of  crystallised  barium  chloride,  dissolved  in  50  c.c. 
of  water  and  the  solution  shaken  and  filtered.     The  filtrate  gives  a  red 
coloration  with  phenolphthalein  if  sodium  hydroxide  is  present.     For  the 
quantitative  determination,  see  17  (below). 

Traces  of  caustic  alkali  are  readily  detected  also  by  moistening  the  sample 
with  a  few  drops  of  Dobbin's  reagent  (yellow  coloration).  This  reagent  is 
prepared  by  adding  to  an  aqueous  solution  of  5  grams  of  potassium  iodide 
a  solution  of  mercuric  chloride  until  a  permanent  precipitate  just  appears  ; 
after  filtration,  I  gram  of  ammonium  chloride  is  added  and  then  dilute 
sodium  hydroxide  solution  until  a  precipitate  is  formed ;  after  filtering 
again,  the  volume  is  made  up  to  i  litre. 

12.  Sodium  Bicarbonate. — A  few  grams  are  heated  at  about  250° 
in  a  test-tube  with  a  delivery-tube  dipping  into  lime  water  :    the  latter 
becomes  turbid  if  bicarbonate  is  present.     Quantitative  determination  is 
made  as  with  Sodium  bicarbonate  (3). 

13.  Sodium   Sulphide.— The    i  :  10   solution  is   either  treated  with 
sodium  nitroprusside  solution   (violet  coloration)  or  acidified  with  dilute 
hydrochloric  acid  and  tested  with  lead  acetate  paper  (brown  coloration). 
For  quantitative  determination,  see  17  (below). 

14.  Sodium  Sulphite. — The  i  :  10  solution,  containing  a  little  starch 
paste,  is  acidified  with  acetic  acid  and  tested  with  dilute  iodine  solution 
(decoloration).     For  quantitative  determination,  see  17  (below). 

15.  Determination  of  the  Moisture  (in  calcined  or  Solvay  soda). — 
5  grams  are  heated  for  30  minutes  at  300°  in  a  platinum  crucible  immersed 
in  a  sand-bath,  cooled  in  a  desiccator  and  weighed. 

16.  Determination  of  the  Strength. 

(a)  CRYSTALLISED  SODA.     5  grams  are  dissolved  in  water  to  i  litre, 
50  c.c.  of  this  solution  (=  2-5  grams  of  substance)  being  titrated  in  the 
cold  with  N-hydrochloric  acid   (methyl  orange),     i  c.c.   N-HC1  =  0-053 
gram  Na2CO3  =  0-143  gram  Na2CO3  +  ioH20. 

(b)  CALCINED  SODA.     Either  of  two  methods  may  be  used. 

1.  English  Method.     26-5  grams  of  substance  are  dissolved  in  hot  water, 
the  liquid  being  made  up  when  cold  to  500  c.c.  and,  if  necessary,  filtered  ; 
50  c.c.   of  the  filtrate  (=2-65  grams  of  substance)   are  titrated  in  the 
cold  with  N-HC1  in  presence  of  methyl  orange  :    i  c.c.  N-acid  =  2%  of 
Na2CO3. 

2.  German  Method  (Lunge's  conditions,  adopted  by  the  German  soda 
manufacturers).     2-65    grams    of    substance,    previously    dehydrated,    are 
dissolved  in  water  and  the  unfiltered  solution  titrated  with  N-HC1  in  presence 
of  methyl  orange  :    i  c.c.  N-acid  =  2%  of  Na2CO3. 

The  value  of  the  soda  is  expressed  in  degrees,  expressing  the  content  in  sodium 
carbonate  or  in  sodium  oxide.  French  or  Gay-Lussac  degrees,  and  also  English 
degrees,  give  the  percentage  of  Na2O  in  the  commercial  soda  ;  English  degrees 
are,  however,  slightly  greater  than  the  French,  the  equivalent  of  sodium  oxide 
being  taken  as  32  instead  of  31.  German  degrees  give  the  content  of  Na2CO3. 
Lastly,  French  Descroizilles  degrees  indicate  the  grams  of  monohydrate  sul- 
phuric acid  (H2SO4)  necessary  to  neutralise  100  grams  of  the  soda,  Thus,  i 


SODIUM  CARBONATE  97 

Gay-Lussac  degree  =  i-oi  English  degree  =  1-71  German  degree  =  1-58  Des- 
croizilles  degree. 

17.  Complete  Analysis. — 100  grams  of  the  soda  are  dissolved  in  a 
beaker  in  hot  water  and  the  liquid  allowed  to  stand  in  the  hot  for  half  an 
hour,  after  which  it  is  filtered  through  a  filter  dried  at  100°  and  tared,  the 
insoluble  matter  being  washed  with  hot  water  and  used  for  determination 
(a).  The  filtrate  is  collected  in  a  litre  flask  and  made  up  to  the  mark  on 
cooling,  being  used  for  the  determinations  (b)  to  (h). 

(a)  INSOLUBLE    RESIDUE.    The   insoluble    matter,    dried   at    100°,    is 
weighed.     It  is  then  moistened  with  water,  lixiviated  with  hot,  dilute  hydro- 
chloric acid  (which  dissolves  the  ferric  oxide,  alumina,  calcium  and  mag- 
nesium carbonates),  washed  with  water,  redried  at  100°  and  weighed  ; 
this  represents  sand  and  carbon  (%).    After  ignition  the  sand  is  weighed 
alone  and  the  carbon  then  obtained  by  difference. 

(b)  TOTAL  ALKALINITY  AND  SODIUM  CARBONATE.    10  c.c.  of  the  solution 
(=i  gram  of  substance),  diluted  with  water,  are  titrated  in  the  cold  with 
N-HC1   (methyl  orange).     This  gives  total  alkalinity,  due  to  carbonate, 
hydroxide  and  sulphide  ;   deduction  from  the  volume  of  acid  used  of  those 
corresponding  to  the  hydroxide  and  sulphide   (determinations  c  and  d] 
and  multiplication  of  the  remainder  by  53  gives  the  grams  of  Na  2CO3  per 
100  grams  of  the  soda. 

(c)  SODIUM  HYDROXIDE.     100   c.c.   of  solution  (=10   grams  of    sub- 
stance) are  shaken  in  a  200  c.c.  flask  with  excess  of  barium  chloride  (10  c.c. 
of  10%  solution  usually  suffice),  made  up  to  volume,  again  shaken  and 
left  to  stand  ;  100  c.c.  of  the  clear  liquid  (not  filtered)  are  pipetted  off  and 
titrated  with  N-hydrochloric  acid  in  presence  of  phenolphthalein.     This 
gives  alkalinity  due  to  hydroxide  and  sulphide  together ;    subtraction  of 
the  corresponding  number  of  c.c.  from  determination  (d]  and  multiplication 
of  the  remainder  by  0-8  gives  percentage  of  NaOH. 

(d)  SODIUM  SULPHIDE.    50  c.c.  of  solution  ( =  5  grams  of  substance) 
are  heated  to  boiling,  treated  with  ammonia  and  ammoniacal  silver  nitrate 
solution  (i3'82  grams  Ag  per  litre)  1  run  in  from  a  burette  until  no  further 
black  precipitate  is  produced.     To  determine  the  end-point  the  more  readily, 
the  liquid  is  filtered  towards  the  end  of  the  titration  and  the  latter  con- 
tinued in  the  filtrate.     The  number  of  c.c.  of  silver  solution,  multiplied 
by  o-i,  gives  the  percentage  of  Na2S  in  the  sample,     i  c.c.  of  silver  solution 
=  0-13  c.c.  of  N-acid  (for  calculations  indicated  in  b  and  c). 

(e)  SODIUM  SULPHITE.    50  c.c.  of  the  solution  (=  5  grams  of  substance) 
are  acidified  with  acetic  acid  and  titrated  with  N/io-iodine  in  presence  of 
starch  paste.     The  number  of  c.c.  used,  multiplied  by  0-1261,  gives  the 
percentage  of  Na2SO3  in  the  sample. 

When  sulphides  are  present,  the  number  of  c.c.  of  iodine  solution  used 
must  be  diminished  by  that  corresponding  with  the  sulphide  found  as  in 
(d),  knowing  that  i  c.c.  of  silver  solution  =  1-3  c.c.  N/io-iodine. 

(/)  SODIUM  CHLORIDE.    With  ammonia    soda,  20  c.c.  (=2  grams  of 

1  13-82  grams  of  pure  silver  are  dissolved  in  nitric  acid,  250  c.c.  of  ammonia  being 
added  and  the  liquid  diluted  to  i  litre,      i  c.c.  of  this  solution  =  0-005  gram  Na2S. 
A.C.  7 


98  SODIUM  CHLORATE 

substance)  or  with  Leblanc  soda,  50  c.c.  (=  5  grams)  of  solution  are  neu 
tralised  exactly  with  N-nitric  acid,  the  liquid  boiled,  10  drops  of  10%  potas- 
sium chromate  solution  added,  and  N/io-silver  nitrate  run  in  from  a  burette 
until  a  red  coloration  appears,     i  c.c.  N/io-silver  nitrate  =  0-005846  gram 
NaCl. 

(g)  SODIUM  SULPHATE.  With  Leblanc  soda,  50  c.c.  (—  5  grams  of 
substance)  or  with  ammonia  soda,  100  c.c.  (  —  10  grams)  of  the  solution 
are  acidified  with  hydrochloric  acid,  heated  to  boiling,  precipitated  with 
barium  chloride,  filtered  and  the  barium  sulphate  washed,  dried,  calcined 
and  weighed  :  i  gram  of  BaSOi  =  0-6089  gram  of  Na2SO4. 

(h)  SILICA  AND  ALUMINA.  100  c.c.  of  the  solution  ( =  10  grams  of 
substance)  are  acidified  with  hydrochloric  acid  and  evaporated  on  a  water- 
bath,  the  residue  being  dried  at  105°  and  taken  up  in  hydrochloric  acid  ; 
the  silica  is  separated  and  weighed,  and  the  alumina  estimated  in  the  solution 
in  the  ordinary  way. 

*  * 

Commercial  soda  crystals  should  contain  at  least  34%  of  Na2CO3  ;  usually 
they  contain  35%  (theoretically  37-042%  Na2CO3  and  62-958%  H2O).  Some- 
times a  slight  excess  of  water  is  present,  but  this  should  not  exceed  i  %  ;  often 
slight  efflorescence  is  shown.  The  ordinary  impurity  is  sulphate  (in  Leblanc 
soda  ;  see  later),  but  large  proportions,  such  as  10-20%,  must  be  regarded  as 
added  artificially.  The  chloride  content  in  Leblanc  soda  should  not  exceed 
0-5%.  The  yellowish  colour  of  certain  soda  crystals  is  usually  derived  from 
organic  substances  and  not  from  iron. 

Calcined  Leblanc  soda  may  contain  small  proportions  of  hydroxide,  sulphide 
and  sulphite,  and  is  often  contaminated  with  sulphate  ;  its  strength  may  vary 
from  80  to  96%,  but  is  most  often  88-95%.  Ammonia  soda  contains  chloride, 
and  sometimes  small  quantities  of  bicarbonate  ;  its  strength  is  95-98%. 

The  moisture  of  calcined  soda  is  usually  0-5-1%,  3%  being  tolerated  ;  in 
moist  air,  calcined  soda  may  absorb  up  to  about  10%  of  moisture. 

The  insoluble  substances  in  ordinary  good  soda  should  not  exceed  0-5%,  of 
which  about  0-1%  is  insoluble  in  hydrochloric  acid  and  0-02%  ferric  oxide. 

The  sulphate  in  ammonia  soda  should  not  be  more  than  0-1%,  if  not  added. 
In  Leblanc  soda  of  best  quality  0-5-1%  occurs,  while  in  inferior  qualities  it 
reaches  8%  or  more. 

The  chloride  occurs  to  the  extent  of  0-5-2-5%  in  ammonia  soda  or  0-25-0-5% 
in  Leblanc  soda. 

Pure  or  chemically  pure  sodium  carbonate  should  answer  all  the  qualitative 
tests,  1-14. 


SODIUM    CHLORATE 

NaClO3  =  106-5 

White  crystals  or  powder  soluble  in  about  i  part  of  cold  water.  The 
commercial  product  does  not  reach  the  degree  of  purity  of  potassium 
chlorate,  but  usually  contains  small  quantities  of  chlorides,  lime  and,  some- 
times, iron.  The  various  impurities  and  also  the  content  of  chlorate  are 
investigated  and  determined  as  in  potassium  chlorate  (q.v.)  :  i  c.c.  N/io- 
thiosulphate  =0-001775  gram  NaC103. 


SODIUM  CHLORIDE  99 

SODIUM    CHLORIDE 

NaCl  =  58-46  (58-5) 

This  is  sold  in  various  degrees  of  purity,  the  most  common  impurities 
being  :  potassium  and  magnesium  chlorides,  sodium,  calcium  and  mag- 
nesium sulphates,  insoluble  substances  (sand,  clay)  and  sometimes  small 
quantities  of  bromides,  iodides,  borates  and  lithium  salts 

Analysis  includes,  therefore,  tests  for  the  above  and  any  other  impurities 
(1-6)  and,  if  the  exact  composition  of  the  salt  is  to  be  known,  certain  quan- 
titative determinations  (7). 

1.  Solubility  and  Various  Impurities. — i  gram  in  10  c.c.  of  water 
should  give  a  clear,  neutral  solution. 

The  i  :  10  solution  is  tested  with  hydrogen  sulphide  (heavy  metals], 
ammonium  sulphide  (iron,  zinc],  ammonium  chloride,  ammonia  and  ammon- 
ium oxalate  (lime}  and,  after  removal  of  any  lime  present,  with  sodium 
phosphate  (magnesium}. 

2.  Potassium  Salts. — These  are  detected  in  the  flame  through  cobalt 
glass,  or  by  dissolving  i  gram  of  substance  in  a  little  water,  adding  platmic 
chloride,  evaporating  on  a  steam-bath,  taking  up  with  50  c.c.  of  80%  alcohol, 
any  yellow,  crystalline  precipitate  formed  immediately  or  after  some  hours 
being  observed. 

3.  Lithium  Salts. — A  few  grams  of  the  finely  powdered  salt  are  moist- 
ened with  90%  alcohol  and  filtered,  the  filtrate  being  examined  in  the  flame 
(through  cobalt  glass)  or  better  through  a  spectroscope. 

4.  Sulphates.— The    i  :  10   solution  is  treated   with   barium  chloride 
in  the  hot  and  the  liquid  examined  after  standing. 

5.  Iodides,  Bromides. — 5  grams  are  moistened  with  a  little  water 
and  filtered  ;  to  the  filtrate  are  added  a  crystal  of  sodiam  nitrite  and  acetic 
acid,  the  whole  being  then  shaken  with  carbon  disulphide,  which  becomes 
violet  or  yellowish  in  presence  of  iodides  or  bromides  respectively. 

6.  Boric  Acid. — 25  grams  are  heated,  with  occasional  shaking,  with 
about  50  c.c.  of  95%  alcohol  acidified  with  hydrochloric  acid  and  filtered, 
the  filter  being  washed  with  a  little  alcohol  and  the  filtrate  rendered  alkaline 
with  sodium  hydroxide  and  evaporated  on  a  steam-bath.     The  residue  is 
taken  up  with  a  little  dilute  hydrochloric  acid  and  the  solution  tested  with 
turmeric  paper  (better,  paper  immersed  in  0-1%  alcoholic  turmeric  solution), 
which  is  then  dried  at  100°  (reddening). 

7.  Quantitative  Determinations. — (a)  MOISTURE.     5  grams  of  the 
salt  are  heated  for  3-4  hours  in  a  dry,  tared  conical  flask  of  about  250  c.c. 
capacity,  with  a  funnel  inserted  in  the  neck,  on  a  sand-bath  at  140-150°. 
The  flask  is  then  allowed  to  cool  in  the  air  on  a  marble  slab  and  reweighed. 

(b)  INSOLUBLE  SUBSTANCES.     10   grams    of    the   salt  are  dissolved  in 
water,  the  solution  being  filtered  through  a  filter  dried  at  100°  and  tared 
The  insoluble  matter  is  washed  with  nearly  half  a  litre  of  water,  dried  at 
100°  and  weighed.     The  filtrate  is  made  up  to  500  c.c.  and  used  for  the 
following  determinations. 

(c)  CHLORINE.     50  c.c.  of  this  solution   (=i  gram  of  salt)  are  titrated 
with  silver  nitrate  in  the  usual  way.     i  c.c.  N/io-AgNO,  =  0-355%  Cl. 


TOO  SODIUM  BICHROMATE 

(d)  SULPHURIC  ACID.     150  c.c.  of  the  solution  ( =  3  grams  of  the  salt) 
are  acidified  with  hydrochloric  acid  and  precipitated  with  barium  chloride, 
the  barium  sulphate  being  filtered,   washed,  dried  and  weighed  as  usual : 

(BaS04  X  34-335)  ^  3  =  %  of  SO3 

(e)  LIME  AND  MAGNESIA.     150  c.c.  of  the  solution  (=  3  grams  of  salt) 
are  treated  with  ammonia  l  and  ammonium  oxalate,  the  calcium  oxalate 
being  ignited  and  the  lime  weighed  :    (CaO  X  100)  ~  3  =  %  or  CaO. 

The  nitrate  from  this  determination  is  treated  with  ammonium  or  sodium 
phosphate  and  the  precipitate  treated  as  usual :  (Mg2P2O7  x  36-036)  ~  3  — 
%  of  MgO. 

(/)  POTASH.  50  c.c.  of  the  solution  (=  i  gram  of  salt)  are  treated  as 
indicated  under  "  Stassfurt  Salts  "  for  the  determination  of  alkalies,  the 
percentages  of  Na2O  and  K2O  being  calculated. 

(g)  CALCULATION  OF  THE  RESULTS.  The  sulphuric  acid  is  combined 
first  with  lime,  then  with  magnesia,  and  lastly,  if  any  remains,  with  potash 
and  then  soda  :  any  remaining  magnesium  is  united  with  chlorine  and  the 
rest  of  the  latter  with  potash  and  then  with  soda. 

* 
*  * 

Chemically  pure  sodium  chloride  should  not  contain  any  of  the  above  impurities. 

The  pure  and  refined  salts  may  contain  respectively  97-98%  and  about 
99-7%  NaCl,  and  always  give  the  reactions  of  sulphates  and  calcium  salts  ;  as 
a  rule  they  contain  traces  only  of  magnesium  salts. 

Common  Salt  (for  domestic  purposes)  varies  in  composition  roughly  between 
the  following  limits  : 

Sodium  chloride         .......  87-96-4% 

Magnesium  chloride  .......  Traces-i-4% 

Magnesium  sulphate.          ......  Traces-i-6% 

Calcium  sulphate       .......  0-3-1-0% 

Sodium  sulphate        .......  0-1-2% 

Water 0-1-10-0% 

Impurities  (insoluble  residue,  etc.)      ....  Traces-o-25% 

Incrustations  from  salt-pans,  known  as  grofo,  contains  less  sodium  chloride 
(77-85%)  than  ordinary  salt  and  also  marked  proportions  of  calcium  sulphate 
(up  to  about  8%),  sodium  sulphate  (up  to  8«4%)and  magnesium  sulphate  (2%). 

Common  salt  generally  contains  small  quantities  of  boric  acid,  this  being 
particularly  the  case  with  certain  salts  of  Italian  origin. 

In  salt  for  soap-boiling,  i%  of  insoluble  impurities  and  2%  of  earthy  salts 
(calcium  and  magnesium  chlorides  and  sulphates)  are  allowed  by  the  Union  of 
Italian  Soapmakers  (1911). 

SODIUM    BICHROMATE 

Na2Cr2O7  +  2H2O  =  298-3  (298) 

The  pure  salt  forms  hygroscopic,  red  crystals,  which  lose  their  water 
of  crystallisation  at  100°.  The  dehydrated  salt  is  also  sold  in  large  quan- 
tities in  fused  masses  or  crusts,  which  are  contaminated  mainly  with  sodium 
sulphate  and  insoluble  carbonaceous  substances.  Its  value  depends  on 
its  content  of  chromic  anhydride.  The  following  tests  are  made  : 

\  If  the  ammonia  produces  a  precipitate  (iron,  aluminium),  this  is  filtered  off  and 
washed  and  the  nitrate  then  treated  as  described. 


SODIUM  NITRTE 


1.  Insoluble  Substances.  —  A  few  grams  are  dissolved  in  water  and 
the  solution  filtered  through  a  tared  filter,  which  is  then  treated  in  the 
ordinary  way. 

2.  Water.  —  -2-3  grams  are  heated  at  100-105°  to  constant  weight. 

3.  Sulphates.  —  Tested  for  as  in  potassium  dichromate  (q.v.)  and  deter- 
mined as  barium  sulphate. 

4.  Determination  of  the  Chromic  Anhydride.  —  As  with  potassium 
dichromate  (q.v.). 

Pure  crystallised  sodium  dichromate  contains  67%  of  CrO3,  and  the  anhydrous 
salt  76-4%.     The  fused  commercial  product  usually  contains  73-74%  CrO3. 


SODIUM    HYDROXIDE  (Caustic  Soda) 

NaOH  =  40 

This  is  sold  in  lumps,  sticks  or  powder,  and  in  various  degrees  of  purity 
(Caustic  soda  from  sodium,  by  alcohol,  by  lime,  purified,  crude).  The  com- 
monest impurities,  often  in  considerable  quantities,  are  carbonates,  sul- 
phates, chlorides,  nitrates,  alumina,  ferric  oxide  and  lime ;  these  are 
detected  as  in  caustic  potash. 

The  strength  is  determined  by  measuring  the  total  alkalinity  and  the 
alkalinity  after  treatment  with  barium  chloride  (methyl  orange  used)  as 
indicated  under  "  Sodium  carbonate  "  :  I  c.c.  N-acid  =  0-04  gram  NaOH 
or  0-031  gram  Na2O  or  0-053  gram  Na2CO3. 


Sodium  hydroxide  pure  from  metal  represents  the  best  quality  sold,  and  should 
contain  only  traces  of  chlorides  and  at  most  5%  of  water. 

Sodium  hydroxide  by  alcohol  should  answer  the  same  requirements  as  potas- 
sium hydroxide  by  alcohol,  and  should  not  contain  more  than  5%  of  water. 

In  sodium  hydroxide  by  lime  the  total  alkalinity  should  not  be  less  than  90% 
and  the  content  of  carbonate  not  greater  than  5%. 

The  strength  of  caustic  soda  for  soap  works  is  usually  expressed  as  Na2O 
(i  c.c.  N-acid  =  0-031  gram  Na2O).  In  that  of  60-65  strength,  3%  of  carbonate 
is  allowable  and  in  that  of  70-77  strength,  1-5%  of  carbonate. 


SODIUM    NITRATE 

See  Fertilisers 

SODIUM    NITRITE 


This  is  sold  in  white  or  yellowish  crystals  or  cast  rods  and  is  extremely 
soluble  in  water  and  moderately  so  in  alcohol.  It  usually  contains  very  few 
impurities  and  its  value  depends  essentially  on  the  content  of  NaN02. 

Quantitative  Determination  (Lunge's  method).  —  A  seminormal 
permanganate  solution  is  prepared  by  dissolving  15-82  grams  of  chemically 
pure  potassium  permanganate  in  water  to  i  litre,  the  titre  being  controlled 


VG?  SODIJM  PHOSPHATE   (DISODIUM  PHOSPHATE) 

by  iron  or  by  oxalic  acid  (i  c.c.  =  0-028  gram  Fe  =  0-0315  gram  crys- 
tallised oxalic  acid). 

10  grams  of  the  nitrite  are  dissolved  in  water  to  i  litre.  20  c.c.  of  the 
permanganate  solution  are  mixed  in  a  conical  flask  with  about  130  c.c.  of 
water  and  a  little  dilute  sulphuric  acid  and  the  liquid  heated  to  40-50°, 
the  nitrite  solution  being  then  run  in  from  a  burette  until  the  colour  dis- 
appears, i  c.c.  N/2-KMnO4  =  0-01725  gram  NaNO2,  so  that  20  c.c.  = 
0-3450  gram,  and  the  percentage  of  nitrite  is  given  by  3450  -f-  n,  where  n  is 
the  number  of  c.c.  of  nitrite  solution  used. 

Commercial  sodium  nitrite  generally  contains  97-99%  of  NaNO2. 

SODIUM    PERBORATE 

NaB03  +  4H20  -  154 

White  powder  or  colourless  crystals,  slightly  soluble  in  cold  but  readily 
in  hot  water  with  liberation  of  oxygen  ;  with  sulphuric  acid  it  gives  hydro- 
gen peroxide.  Its  value  depends  essentially  on  the  content  of  actual  per- 
borate or  active  oxygen,  which  is  determined  with  permanganate  as  in 
barium  peroxide  (q.v.).  i  c.c.  N/5-permanganate  =  0-01483  grain  of 
NaB03  +  4H2O  =  0-0016  gram  of  oxygen. 

Commercial  sodium  perborate  is  usually  guaranteed  to  contain  10%  of  active 
oxygen  (theoretically  10-4%). 

SODIUM    PEROXIDE 

Na2O2  =78 

Hygroscopic  white  or  yellowish  powder,  decomposed  by  water  with 
evolution  of  oxygen.  It  may  contain,  as  impurities,  sodium  hydroxide 
and  carbonate,  sulphates,  chlorides,  phosphates,  iron  and  alumina,  which 
may  be  detected  by  the  tests  indicated  under  "Potassium  Hydroxide.'' 
Its  value  depends  on  the  content  of  Na202,  which  may  be  determined 
sufficiently  exactly  for  technical  purposes  by  titration  with  permanganate 
(see  Barium  Peroxide),  but  the  peroxide  must  be  added  to  the  sulphuric 
acid  with  great  care,  i  c.c.  N/5-permanganate  =  0-0078  gram  Na.,O2. 

An  exact  determination  may  be  made  by  Archbutt  and  Grossmann's 
method,  which  consists  in  decomposing  the  peroxide  with  water  in  presence 
of  a  little  cobalt  nitrate  and  measuring  the  volume  of  oxygen  evolved, 
Lunge's  nitrometer  or  gas-volumometer  or  similar  apparatus  being  used.1 

Commercial  sodium  peroxide  (well  stored)  contains  on  the  average  95%  of 
Na2O2  ;  its  content  in  Fe2O3  +  A12O3  should  not  exceed  0-01%. 

SODIUM    PHOSPHATE  (Disodium  Phosphate) 

Na2HP04+  i2H20  -358-3 

Colourless,  readily  efflorescent,  more   or  less  large  crystals,  soluble  in 
water  to  a  faintly  alkaline  solution.     The  commoner  impurities  are  car- 
1  See  Analyst,  1895,  p.  3  ;    Chem.  Zeitung,  1905,  p.   138. 


SODIUM  SILICATE   (WATER  GLASS)  103 

bonates,  chlorides,  sulphates  and  arsenic  (tests  1-4).     The  content  in  phos- 
phate may  be  deduced  from  the  determination  of  the  phosphoric  acid  (5). 

1.  Solubility. — i  part  in  10  of  water  should  give  a  clear,  colourless 
solution. 

2.  Carbonates. — Any  evolution  of  gas  noted  on  dropping  a  few  crystals 
into  dilute  hydrochloric  acid. 

3.  Chlorides,  Sulphates  .—The  i  :  10  solution,  acidified  with  dilute 
nitric  acid,  is  tested  with  silver  nitrate  or  barium  chloride. 

4.  Arsenic. — i  gram,  with  5  c.c.  of  Bettendorf's  reagent,  should  give 
no  coloration  within  an  hour. 

5.  Determination  of  the  Phosphoric  Acid. — 25  grams  are  dissolved 
in  water  to  i  litre  and  in  20  c.c.  of  this  solution  (  =  0-5  gram  of  substance) 
the  phosphoric  acid  precipitated  with  magnesia  mixture   (see  Fertilisers  : 
Determination  of  Phosphoric  Acid,  A)  and  the  magnesium  pyrophosphate 
weighed  as  usual  :    i  gram  Mg2P2O7  =  3-216  grams  Na,HPO4  +  I2H2O  = 
0-6376  gram  P2O5. 

Commercial  sodium  phosphate  of  good  quality  contains  about  98%  Na2HPO4 
+  i2H2O  or  19-4-19-5%  P2O5. 


SODIUM    SILICATE  (Water  Glass) 

This  has  no  well  defined  and  constant  composition,  but  usually  consists 
of  a  mixture  of  sodium  tri-  and  tetra-silicates,  Na2Si3O7  and  Na2Si409. 
It  is  sold  as  a  colourless,  yellowish  or  greenish  solution  (30-33°,  37-40°  or 
50°  Baume),  or  in  powder  or  glass-like  masses.  It  dissolves  in  water  (the 
solid,  containing  a  large  excess  of  silica,  only  with  difficulty),  the  aqueous 
solution  giving  a  gelatinous  precipitate  of  silica  with  acids. 

In  either  the  liquid  or  solid  form,  chlorides,  sulphates,  alumina  and 
insoluble  substances  should  be  tested  for,  and  the  silica  and  alkali  deter- 
mined : 

1.  Solubility. — 20  grams  diluted  to  500  c.c.  should  give  a  clear  liquid 
which  does  not  become  turbid  after  some  days. 

2.  Chlorides,  Sulphates. — 1-2  grams,  diluted  with  100  c.c.  of  water, 
acidified  with  nitric  acid  and  filtered,  is  tested  with  silver  nitrate  or  barium 
chloride. 

3.  Alumina,  Ferric  Oxide,  etc. — 2  grams  are  evaporated  with  excess 
of  cone,  hydrochloric  acid  and  the  residue  dried  at  120°  to  render  the  silica 
insoluble.     The  residue  is  taken  up  in  dilute  hydrochloric  acid,  the  solution 
filtered  and  the  filtrate  tested  for  aluminium,  iron,  and  any  lime  or  other 
extraneous  substance. 

4.  Quantitative  Determinations. — 100  grams  are  diluted  with  water 
to  i  litre  and  the  solution  used  for  the  following  determinations  : 

(a)  TOTAL  ALKALI.     50  c.c.  (=  5  grams  of  substance)  are  titrated  with 
N-hydrochloric  acid  in  presence  of  methyl  orange  :  i  c.c.  N-acid  —  0-031 
gram  Na2O. 

(b)  SILICA.    50  c.c.  (=  5  grams  of  substance)  are  decomposed  with  cone. 
HC1  in  a  platinum  dish,  the  liquid  being  evaporated  to  dryness,  the  residue 


104  SODIUM  STANNATE 

heated  for  about  2  hours  at  110-120°,  treated  with  dilute  hydrochloric  acid, 
and  the  silica  filtered  off,  washed,  dried,  ignited  and  weighed. 

In  the  hydrochloric  acid,  the  alumina,  sodium  chloride,  etc.,  may  be 
determined. 

(c)  FREE  ALKALIES.  To  100  c.c.  of  the  solution  (=  10  grams  of  sub- 
stance) are  added,  in  a  thin  stream  and  with  constant  shaking,  100  c.c.  of 
10%  barium  chloride  solution,  the  liquid  being  made  up  to  250  c.c.,  shaken 
and  filtered  through  a  dry  paper.  The  first  20-30  c.c.  of  the  filtrate  are 
rejected  and  in  100  c.c.  of  the  remainder  (=4  grams  of  substance)  the  free 
alkali  is  titrated  with  N/io-hydrochloric  acid  in  presence  of  phenol- 
phthalein  :  i  c.c.  N/io-acid  =  0-004  gram  NaOH. 

Potassium  silicate  is  analysed  similarly. 

In  commercial  sodium  silicate  of  good  quality  the  ratio  of  Na2O  to  SiO2  is' 
about  3  :  i,  while  free  alkali  is  found  only  in  small  quantity  (less  than  0-5%) 
and  the  extraneous  impurities  do  not  total  2%. 


SODIUM    STANNATE 

Na2SnO3  +  3H2O  =  267 

Hard  white  crystals  or  crystalline  masses,  somewhat  efflorescent,  soluble 
in  water  (in  the  air  the  solution  becomes  cloudy  owing  to  formation  of 
oxide  of  tin),  insoluble  in  alcohol.  Its  commoner  impurities  are  sodium 
carbonate,  hydroxide,  chloride  and  sulphate,  and  iron.  Double  salts,  con- 
sisting of  sodium  stannate  and  arsenate,  or  sodium  tungstate  and  stannate, 
are  also  sold.  Analysis  includes  the  following  : 

1.  Solubility. — i  gram,  with  10  c.c.  of  water,  should  give  a  clear  or 
barely  opalescent  solution. 

2.  Sodium  Carbonate  and  Hydroxide. — A  few  fragments,  dropped 
into  dilute  hydrochloric  acid,  should  give  no  effervescence  (carbonate),  and 
if  the  substance  is  dissolved  in  a  little  water  and  then  shaken  with  absolute 
alcohol,  the  liquid  should  not  have  an  alkaline  reaction  (hydroxide). 

3.  Chlorides,  Sulphate,  Iron. — 2  grams  are  dissolved  in  10  c.c.  of 
water,  acidified  with  nitric  acid  and  filtered  :    the  filtrate  is  tested  with 
silver  nitrate  (chlorides),  barium  chloride  (sulphates)  and  ammonium  thio- 
cyanate  (iron). 

4.  Sodium  Arsenate. — i  gram  is  heated  in  a  porcelain  dish  with  5  c.c. 
of  nitric  acid  (i  :  i)  on  a  steam-bath  and  evaporated  to  dryness,  the  residue 
being  taken  up  in  water  and  a  few  drops  of  nitric  acid  and  the  liquid  fil- 
tered.    To  the  filtrate  is  added  an  excess  of  silver  nitrate,  the  liquid  again 
filtered  if  necessary  and  very  dilute  ammonia  poured  carefully  on  to  the 
clear  filtrate  :  in  presence  of  arsenate,  a  reddish  ring  forms  at  the  zone  of 
contact  of  the  two  liquids. 

5.  Sodium  Tungstate..— 1-2  grams  are  dissolved  in  10  c.c.  of  water 
and  the  liquid  filtered  and  treated  with  excess  of  hydrochloric  acid  :    in 
presence  of  tungstate  a  yellowish  white  gelatinous  precipitate  is  formed  which 
becomes  blue  when  heated  gently  with  a  very  small  quantity  of  zinc  dust. 

6.  Determination  of  the  Alkali.— 10  grams  are  dissolved  in  water 


SODIUM  SULPHATE  105 

to  100  c.c.  ;  10  c.c.  of  the  solution  (  =  i  gram  of  substance)  are  titrated  with 
N-alkali  in  presence  of  methyl  orange  :  i  c.c.  N-alkali  =  0-031  gram  Na2O. 
If  the  total  Na2O,  thus  obtained,  is  diminished  by  the  quantity  corre- 
sponding with  the'  stannic  oxide  found  (i  part  of  SnO2  requires  0-4106 
part  of  Na2O),  the  free  alkali  is  obtained. 

7.  Determination  of  the  Tin. — i  gram  is  dissolved  in  water  and  hydro- 
chloric acid,  the  solution  being  then  allowed  to  react  with  a  few  pure  alumi- 
nium turnings  for  about  half  an  hour  in  the  cold.  The  liquid  is  then  heated 
with  a  further  quantity  of  cone,  hydrochloric  acid  in  a  current  of  carbon 
dioxide  until  the  spongy  tin  which  has  separated  completely  redissolves  ; 
the  subsequent  procedure  is  as  indicated  under  "  Stannous  Chloride  " 
(quantitative  determination). 

*  * 

Commercial  sodium  stannate  is  never  completely  soluble  in  water,  but  it  is 
required  to  dissolve  to  as  great  an  extent  as  possible.  The  percentage  of  tin 
may  vary  from  30  to  44  (theoretical,  44-85),  equal  to  38-56%  SnO2.  The  con- 
tent in  free  alkali  may  be  variable  (up  to  5%),  as  also  may  the  proportions  of 
chloride,  sulphate,  arsenate  and  tungstate  (commercial  stannates  have  been 
met  with  containing  2-50%  of  sodium  chloride  and  15-20%  of  arsenate). 

For  dyeing  purposes,  absence  of  iron  and  little  free  alkali  are  particularly 
required. 

SODIUM    SULPHATE 

Na2SO4  +  ioH2O  =  322  ;    Na2SO4  =  142 

The  pure  salt  forms  colourless  crystals  (+  ioH20),  soluble  in  about  3 
parts  of  cold  water.  The  crude  salt  for  technical  purposes  is  also  sold  and 
forms  white  or  yellowish  anhydrous  powder  or  fused  masses..'  The  more 
common  impurities  are  :  sodium  chloride  and  bisulphate,  magnesium,  cal- 
cium and  ammonium  salts,  arsenic,  heavy  metals  and  insoluble  substances. 
For  the  analysis  of  the  crystallised  salt  it  is  usually  sufficient  to  test  for 
the  above  impurities  by  the  methods  indicated  under  "  Potassium  Sul- 
phate "  (the  arsenic  test  is  made  on  i  gram  dissolved  in  3  c.c.  of  water, 
which  should  not  give  a  brown  coloration  with  5  c.c.  of  Bettendorf  's  reagent 
within  an  hour).  With  the  crude  salt,  the  following  determinations  are 
made  : 

1.  Moisture. — 2-3  grams  are  gently  ignited  and  reweighed. 

2.  Free  Acid  (bisulphate). — 20  grams  are  dissolved  in  water  to  250  c.c., 
50  c.c.  of  the  solution  (=4  grams  of  substance)  being  titrated  with  N-alkali 
in  presence  of  methyl  orange  :   i  c.c.  N-alkali  corresponds  with  i%  S03. 

3.  Sodium  Chloride. — 50  c.c.  of  the  solution  (=  4  grams  of  substance) 
are  neutralised  exactly  with  N-alkali  (the  quantity  necessary  is  known  from 
test  2),  a  little  potassium  chromate  added  and  the  liquid  titrated  with  N/io- 
silver  nitrate.     Each  c.c.  of  N/io-AgN03  corresponds  with  0-146  %  NaCl. 

4.  Iron. — 10  grams  are  dissolved  in  water  and  the  solution  treated  with 
sulphuric  acid  and  pure  zinc,  the  iron  thus  reduced  being  titrated  with  per- 
manganate in  the  ordinary  way.     If  the  iron  is  present  in  very  small  pro- 
portion, the  colorimetric  method  used  with  aluminium  sulphate  may  be 
employed. 


io6  SODIUM  SULPHIDE 

5.  Insoluble  Substances.— 10-20  grams  are  dissolved  in  a  little  water, 
the  insoluble  matter  being  filtered  off,  washed,  dried,  ignited  and  weighed. 

6.  Alumina.- — -The  nitrate  from  the  preceding  operation  is  heated  with 
a  little  ammonium  chloride  and  ammonia  quite  free  from  carbonate,  the 
precipitate  being  filtered  off,  washed,  dried,  ignited  and  weighed  as  A12O3 
+  Fe2O3.     The  proportion  of  iron  being  known   from  determination  4, 
that  of  the  alumina  may  be  calculated. 

7.  Lime. — The  filtrate  from  the  alumina  is  precipitated  with  ammonium 
oxalate,  the  calcium  oxalate  beingweighed  in  the  usual  way  as  calcium  oxide. 

8.  Magnesia. — To  the  filtrate  from  the  preceding  operation   (some- 
what concentrated  if  necessary),  ammonia  and  sodium  phosphate  are  added ; 
after  24  hours  the  precipitate  is  filtered  off,  washed  with  slightly  ammoniacal 
water,  dried,  ignited  and  weighed  as  magnesium  pyrophosphate  :  i  part 
of  the  latter  =  0-36242  part  of  MgO. 

9.  Quantitative  Determination  of  the  Sodium  Sulphate. — igram 
of  the  sulphate,  dissolved  in  water,  is  treated  with  ammonia  and  ammonium 
carbonate  to  precipitate  alumina,  iron  and  lime,  the  liquid  being  then 
filtered  and  the  nitrate  evaporated  to  dryness  with  a  few  drops  of  pure  sul- 
phuric acid  in  a  tared  platinum  dish  ;  the  residue  is  ignited,  at  first  alone 
and  later  with  a  few  crystals  of  pure  ammonium  carbonate,  and  weighed. 
The  weight  is  diminished  by  that  of  the  sodium  sulphate  corresponding 
with  the  sodium  chloride  found  (in  3)  (i  part  NaCl  =  1-2136  Na2SO4)  and 
by  that  of  the  magnesium  sulphate  corresponding  with  the  magnesia  found 
(in  8)   (i  part  MgO  =  2-9836  MgSO4)  ;  the  remainder  gives  the  Na2SO4 

present  in  i  gram  of  substance. 

* 
*   * 

Crystallised  sodium  sulphate  should  contain  44-1%  Na2SO4  and  55-9% 
H2O,  but  usually  it  is  somewhat  effloresced  and  the  percentage  of  water  rather 
low  ;  the  commonest  impurity  is  a  small  amount  of  the  chloride. 

The  crude  anhydrous  sulphate  generally  contains  1-2%  of  moisture,  its 
free  acidity  being  often  above  i%  and  the  content  of  iron  usually  0-03-0-15%, 
but  sometimes  0-5%  (0-15%  is  allowable)  ;  the  proportions  of  insoluble  matter, 
sodium  chloride,  alumina,  lime  and  magnesia  vary. 


SODIUM    SULPHIDE 

Na2S  +  gH2O  =  240 

Deliquescent,  colourless  or  more  often  greenish  or  yellowish  crystals, 
extremely  soluble  in  water.  The  calcined  (anhydrous)  product  is  also  sold 
in  grey  or  brown,  irregular  masses  soluble  in  water.  The  most  frequent 
impurities  are  :  carbonaceous  particles,  ferric  sulphide,  sodium  thiosulphate 
and  sulphate  and  free  alkali  (tests  1-3) ;  the  content  of  Na2S  is  found  as  in  4. 

1.  Solubility. — 5  grams  should  give  a  clear  solution  in  50  c.c.  of  water. 
If  it  does  not  do  so  (presence  of  carbon,  ferric  sulphide],  the  liquid  is  filtered 
through  a  filter  previously  dried  at  105°  and  tared  and  the  insoluble  matter 
washed  well  with  tepid  water,  dried  at  105°  and  weighed. 

2.  Thiosulphate,  Sulphate. — 2  grams  are  dissolved  in  a  little  water 
and  treated  with  excess  of  dilute  hydrochloric  acid,  any  turbidity  indicating 


SODIUM  SULPHITE  107 

thiosulphate  ;    the  hydrogen  sulphide  is  then  expelled  by  boiling  and  the 
liquid,  first  filtered  if  necessary,  tested  with  barium  chloride  (sulphate}. 

3.  Free  Alkali. — 5  grams  are  dissolved  in  water  and  titrated  with  N/io- 
hydrochloric   acid  in   presence  of  phenolphthalein  :     I   c.c.   N/io-acid  = 
0-0040  gram  NaOH. 

4.  Determination   of  the   Sodium   Sulphide    (Battegay's  method). 
— 50  grams  are  dissolved  in  water  to  i  litre  and  50  c.c.  of  this  solution  (  =  2-5 
grams  of  substance)  neutralised  with  acetic  acid  towards  phenolphthalein 
(disappearance  of  the  red  colour)  and  then  titrated  with  N/2-zinc  sulphate 
(71-8425  grams  ZnSO4  +  7H2O  per  litre)  until  a  drop  of  the  liquid  no  longer 
forms  a  yellow  spot  when  placed  on  thick  absorbent  paper  (not  ordinary 
filter-paper)  steeped  in  concentrated  cadmium  sulphate  solution  :  I  c.c . 
N/2-zinc    sulphate    solution  =  0-06    gram    Na2S  +  9H2O  =  0-0195    gram 
Na2S. 

Commercial  crystallised  sodium  sulphide  is  usually  pure,  or  almost  so,  but 
the  calcined  product  contains  more  or  less  marked  proportions  of  insoluble 
residue,  thiosulphate,  sulphate  and  free  alkali. 


SODIUM    SULPHITE 

Na2S03  +  7H20  =  254 

Colourless  crystals  soluble  in  4  parts  of  cold  water  to  a  neutral  solution. 
It  may  contain  carbonates,  bisulphites,  thiosulphates,  sulphates,  chlorides, 
and  traces  of  iron  and  arsenic  (tests  1-7).  Its  value  depends  on  the  content 
of  sulphite  (8). 

1.  Carbonates. — If  sodium  carbonate  is  present,  the  aqueous  solution 
has  an  alkaline  reaction  towards  litmus  paper,  and  addition  of  lime  water 
yields  a  white  turbidity  or  precipitate. 

2.  Bisulphites,  Thiosulphates. — In  presence  of  bisulphite  the  solu- 
tion is  acid.     If  thiosulphate  is  present,  sulphur  is  separated  on  addition  of 
hydrochloric  acid. 

3.  Sulphates. — The  solution  is  boiled  with  excess  of  HC1  to  expel 
sulphurous  acid  and  tested  with  barium  chloride.     It  is  very  difficult  to 
obtain  the  sulphite  free  from  traces  of  sulphate. 

4.  Chlorides. — The  solution  is  boiled  with  excess  of  nitric  acid  and 
tested  with  silver  nitrate. 

5.  Arsenic. — 5  grams  are  evaporated  to  dryness  with  pure  cone.  H2SO4 
and  the  residue  dissolved  in  water  and  tested  in  the  Marsh  apparatus  or  with 
hydrogen  sulphide. 

6.  Iron. — -The  I  :  10  solution  is  boiled  with  a  few  drops  of  cone.  HNO3, 
then  diluted  somewhat  and  tested  with  ammonium  thiocyanate. 

7.  Metals,   Earths. — In  absence  of  metals  and  alkaline  earths,   the 
solution    should    show    no    change   with   ammonium  sulphide,   ammonia, 
ammonium  oxalate  or  sodium  phosphate. 

8.  Quantitative  Determination. — See  Sodium  Bisulphite. 


io8  STANNIC  CHLORIDE 

SODIUM    THIOSULPHATE  (Hyposulphite) 

Na2S203  +  5H20  =  248-3 

Colourless  crystals,  soluble  in  water  to  a  neutral  solution.     It  may  con- 
tain sulphides,  sulphates,  sulphites,  carbonates  and  chlorides. 

1.  Sulphides. — With  lead  acetate  the  solution  gives  an  immediate 
black  coloration  or  precipitate  in  presence  of  sulphide. 

2.  Sulphates,    Sulphites,    Carbonates. — A   solution   of   i   gram   in 
30  c.c.  of  water  should  not  be  rendered  turbid  by  barium  chloride  or  give 
a  red  coloration  with  phenolphthalein  (sodium  carbonate}. 

3.  Chlorides. — The  i  :  10  solution  is  boiled  with  excess  of  nitric  acid, 
filtered  and  tested  with  silver  nitrate. 

4.  Quantitative  Determination. — 20  grams  are  dissolved  to    i  litre 
and  20   c.c.    of   the   solution  (=  0-4  gram   of    substance)     titrated   with 
N/io-iodine  in  presence  of  starch  paste  :  i  c.c.  N/io-iodine  =0-0248  gram 

,  +  5H/X1 


SODIUM    TUNGSTATE 

Na2WO4  +  2H20  =  330 

Colourless  crystals  or  white  or  yellowish  powder  soluble  in  about  4  parts 
of  cold  water,  and  often  containing  excess  of  alkali.  Its  value  depends  essen- 
tially on  the  content  of  tungstic  acid,  which  may  be  determined  as  follows  : 

Determination  of  the  Tungstic  Acid. — 1-2  grams  are  dissolved  in 
a  little  water  and  any  excess  of  alkali  neutralised  with  nitric  acid  in  presence 
of  phenolphthalein,  cone,  mercurous  nitrate  solution  being  then  added  until 
no  further  formation  of  precipitate  takes  place.  After  thorough  shaking 
and  heating  to  cause  the  mercuric  tungstate  to  settle  well,  the  liquid  is 
filtered  and  the  precipitate  washed  with  dilute  mercurous  nitrate  solution, 
dried  at  100°,  ignited  (under  a  hood  on  account  of  the  mercury  vapour 
evolved)  and  weighed  as  tungstic  anhydride  :  i  part  W03  =  1-4224  parts 
of  Na2WO4  +  2H2O. 


STANNIC    CHLORIDE 

SnCl4  =  261 ;    SnCl4  +  5H2O  =  351 

This  is  sold  as  :  Anhydrous  stannic  chloride,  heavy,  colourless  liquid 
emitting  dense  white  fumes  in  the  air,  D  =  2-26,  b.pt.  115°  ;  Liquid  stannic 
chloride,  colourless  or  yellowish  aqueous  solution  of  the  anhydrous  salt, 
50-60°  Baume  ;  Solid  stannic  chloride  (SnCl4  +  5H2O)  in  white  or  yellowish, 
hygroscopic  crystalline  masses. 

The  commonest  impurities  consist  of  free  chlorine,  nitric  and  sulphuric 
acids,  stannous  chloride,  stannic  oxide,  ammonium,  lead,  iron  and  alkali 
salts  (especially  NaCl). 

1  See  also  Sodium  Bisulphite. 


STANNIC  CHLORIDE  109 

1.  Impurities   in   general. — When  the  aqueous  solution  is  treated 
with  hydrogen  sulphide  and  filtered,  the  filtrate  should  leave  no  appreciable 
residue  on  evaporation. 

2.  Free  Chlorine. — The  i  :  10  solution  is  treated  with  iodide-starch 
paste. 

3.  Sulphuric  Acid. — The  I  :  10  solution  is  tested  with  barium  chloride, 
the  barium  sulphate  being  weighed  if  necessary. 

4.  Nitric  Acid. — The  concentrated  solution  is  tested  with  sulphuric 
acid  and  ferrous  sulphate. 

5.  Stannous  Chloride. — The  i  :  10  solution  is  tested  with  mercuric 
chloride  (white  or  grey  precipitate).     Quantitative  determination  as  under 
"  Stannous  Chloride." 

6.  Stannic  Oxide  (Metastannic  Acid). — This  is  indicated  by  an  insoluble 
white  deposit  in  the  liquid  chlorides.     The  solid  chloride  (1-2  grams)  is 
treated  with  excess  of  sodium  hydroxide,  which  will  dissolve  it  completely 
in  absence  of  the  oxide. 

7.  Ammonia. — The   i  :  10  solution  is  boiled  with  excess  of  sodium 
hydroxide. 

8.  Lead. — The  precipitate  formed  by  hydrogen  sulphide   (test  i)   is 
treated  with  yellow  ammonium  sulphide  :   in  presence  of  lead  an  insoluble 
black  residue  remains. 

9.  Iron. — The  i  :  10  solution,  acidified  with  HC1,  is  tested  with  a  few 
drops  of  potassium  thiocyanate  (red  coloration). 

10.  Alkali  Salts   (Sodium  Chloride). — These  are  detected  by  test  i. 
For  quantitative  determination,  i  gram  of  substance  is  dissolved  in  about 
500  c.c.  of  water  and  the  liquid  boiled  to  complete  decomposition  of  the 
stannic  chloride  into  the  oxide  and  filtered,  the  precipitate  being  washed 
and  the  total  filtrate  evaporated  to  dryness,  dried  at  120°  and  weighed.1 

11.  Determination  of  the  Tin  and  Hydrochloric  Acid. — i  gram  of 
substance  is  boiled  with  500  c.c.  of  water  as  in  test  lo.1    The  insoluble  part 
is  collected  on  a  filter,  washed,  dried,  ignited  and  weighed  as  SnO2.     i  part 
Sn02  —  0-78808  part  of  Sn. 

The  nitrate  is  titrated  with  N  alkali  in  presence  of  phenolphthalein. 
i  c.c.  N-alkali  =0-0365  gram  HC1  or  0-0355  gram  Cl. 

* 
*   * 

Stannic  chloride  of  good  quality  should  contain  only  small  proportions  of  the 
above  impurities.  The  content  of  SO3  should  not  exceed  0-04%,  and  iron 
should  be  only  in  traces.  The  solid  chloride  should  contain  not  less  than  45-4% 
Sn.  Sodium  chloride  often  occurs  to  the  extent  of  5%  or  more. 

The  so-called  Tin  Compounds  or  Solutions,  Tin  mordants,  Nitromuriates  or 
Sulphomuriates  of  Tin  consist  of  solutions  of  stannic  and  Stannous  chlorides 
with  varying  proportions  of  sulphuric  and  nitric  acids,  ammonium,  zinc  or  iron 
salts,  sodium  chloride,  etc.  ;  their  value  depends  mainly  on  the  proportion  of 
total  tin  present. 

1  If  Stannous  salts  are  present,  a  little  bromine  water  is  added  prior  to  the  boiling. 


no  SULPHUR 

STANNOUS    CHLORIDE 

SnCl2  +  2H2O  =  226 

White  or  yellowish  crystals,  soluble  in  water,  alterable  in  moist  air. 
It  may  contain,  as  impurities,  oxychloride  (insoluble),  iron,  etc.  (see  Stannic 
Chloride),  and  maybe  adulterated  with  sodium  chloride  or  sodium,  mag- 
nesium or  zinc  sulphate.  These  impurities  are  detected  as  in  stannic  chloride 
(tests  i,  3,  7,  8  and  9).  The  presence  of  oxychloride  is  indicated  by  the 
incomplete  solubility  of  the  salt  in  water  and  in  alcohol. 

Its  value  depends  essentially  on  the  proportion  of  tin  in  the  stannous 
condition,  determinable  as  follows  : 

Quantitative  Determination  (Goppel  and  Frankel's  method). — -3-4 
grams  of  the  chloride  are  dissolved  in  30-40  c.c.  of  10%  hydrochloric  acid 
and  the  liquid  diluted  to  500  c.c.,  50  c.c.  of  the  solution  being  then  treated, 
in  a  bottle  with  a  ground  stopper,  with  50  c.c.  N/io-K2Cr2O7.  After  15 
minutes,  10-15  c-c-  °f  potassium  iodide  solution  and  5-10  c.c.  of  hydro- 
chloric acid  (both  I  :  10)  are  added,  and,  after  a  further  half  an  hour,  the 
liquid  is  diluted  with  200  c.c.  of  water  and  the  iodine  liberated  titrated  with 
N/io-thiosulphate  and  starch  paste.  The  difference  in  c.c.  between  the 
volumes  of  dichromate  and  thiosulphate,  multiplied  by  0-0113  gives  the 
amount  of  SnCl2  +  2H2O,  and  multiplied  by  0-00595  the  amount  of  tin 
in  the  quantity  of  substance  taken  for  titration. 

Stannous  chlorides  of  99-100%  and  of  96-8-98-7%  are  now  sold,  the  latter 
being  guaranteed  to  contain  51-52%  Sn.  Adulteration  with  zinc  or  magnesium 
sulphate  is  now  rare. 


SULPHUR 

S  =  32-07  (32) 

Native  or  mineral  sulphttr,  consisting  of  sulphur  mixed  with  varying 
proportions  of  gangue  (chalk,  gypsum,  clay,  bituminous  matter),  is  the  raw 
material  from  which  the  bulk  of  the  sulphur  of  commerce  is  derived.  The 
latter  is  divided  into  :  Crude  sulphur  of  ist,  2nd  and  3rd  qualities,  in  lemon- 
yellow  loaves,  which  are  more  or  less  shining,  pale  and  opaque  according  to 
the  grade  ,  Refined  sulphur,  in  loaves,  sticks  or  powder  (Ground  and  sieved 
sulphur],  bright  lemon-yellow  and  shining ;  Sublimed  sulphur  or  Flowers 
of  sulphur,  a  fine,  light,  yellowish  powder.  Further,  Magister  of  sulphur 
or  precipitated  sulphur  (obtained  by  treating  calcium  sulphide  solution  with 
hydrochloric  acid),  for  pharmaceutical  uses,  forms  a  very  fine,  light,  amor- 
phous powder  of  dirty  yellowish-white  colour ;  finally,  Coppered  sulphur, 
for  agricultural  uses,  is  a  mixture  of  winnowed  sulphur  with  0*5-5%  (usually 
3-5%)  of  copper  sulphate. 

For  certain  purposes  (manufacture  of  sulphuric  acid),  iron  pyrites  may 
be  regarded  as  a  sulphur  mineral  and  will  be  considered  here.  These 
substances  are  examined  as  follows  : 


SULPHUR  in 

1.    Sulphur  Mineral 

The  essential  determination  is  that  of  the  sulphur  content.  The  sample 
should  be  as  representative  as  possible  of  the  bulk  and  should  be  at  least 

5  kilos,  this  being  finely  powdered  and  well  mixed. 

Determination  of  the  Moisture  and  of  the  Sulphur. — 5-10  grams 
are  heated  in  a  porcelain  dish  at  100°  to  constant  weight  ;  the  loss  represents 
moisture.  The  dry  sulphur  is  then  placed  in  a  filter-paper  cartridge  (finger) 
and  extracted  with  pure  carbon  disulphide  (free  from  residue)  in  a  Soxhlet 
apparatus.  The  solution  is  evaporated  carefully  (carbon  disulphide  being 
inflammable)  and  the  residue  dried  at  70-80°  and  weighed.  This  gives  the 
sulphur  content  provided  that  the  mineral  contains  no  appreciable  amount 
of  bituminous  substances. 

The  latter  are  soluble  in  carbon  disulphide  and  yield  a  brown  or  blackish 
deposit  on  the  walls  and  bottom  of  the  vessel  (see  Crude  sulphur,  i).  In 
such  case  the  sulphur  in  the  extract  is  determined  by  one  of  the  follow- 
ing methods  x : 

(a)  FRESENIUS  AND  BECK'S  METHOD.    This  method  requires  at  least 
10  grams  of  residue   (sulphur  and  bitumen)  from  the  carbon  disulphide 
extract. 

8-10  grams  of  the  residue  are  weighed  into  a  porcelain  crucible  glazed 
inside  and  outside,  this  crucible  being  then  placed  inside  a  second  only 
slightly  larger,  immersed  to  its  rim  in  a  sand-bath.  The  temperature  of  the 
sand  is  then  maintained  at  200-220°  for  7-8  hours  and  the  crucible  weighed 
when  cool.  After  a  further  hour's  heating,  the  crucible  is  again  weighed, 
this  being  repeated  until  no  loss  of  weight  occurs. 

The  loss  of  weight  at  200°  represents  the  sulphur.  The  residue  in  the 
crucible  is  then  ignited  until  all  carbonaceous  matter  disappears,  the  new 
loss  of  weight  giving  the  bitumen. 

(b)  MANZELLA  AND  LEVI'S  METHOD.    This  method  requires  a  conical 
flask  of  about  100  c.c.,  with  a  ground-in  air-condenser  tube  40  cm.  long  and 

6  mm.  bore,  the  whole  being  of  Jena  glass. 

0-2  gram  of  the  residue  from  the  carbon  disulphide  extraction  is  weighed 
into  the  flask,  the  tube  fitted  into  place  and  the  flask  immersed  in  cold 
water.  Through  the  inclined  tube,  10  c.c.  of  fuming  nitric  acid  (D  —  1-52) 
and  5  drops  of  bromine  are  introduced  and  the  flask  shaken  until  'most  of 
the  sulphur  and  bromine  are  dissolved,  5  c.c.  of  fuming  nitric  acid  being 
then  added  and  the  flask  again  shaken  for  some  time.  The  flask  is  then 
heated  gently  (the  water  not  boiling)  in  a  water-bath  for  about  half  an  hour. 
The  flask  is  again  immersed  in  the  cold  water  and  50  c.c.  of  cold  water  added, 
by  the  tube,  drop  by  drop  to  avoid  any  violent  evolution  of  red  vapourt. 
The  solution  is  then  transferred  to  a  porcelain  dish  together  with  the  wash- 
ings of  the  flask  and  tube  and  evaporated  to  a  small  volume,  a  few  drops  of 
cone,  hydrochloric  acid  being  added  and  the  liquid  again  evaporated.  The 
residue  is  taken  up  in  water  and  made  up  to  400-500  c.c.  in  a  beaker,  the 
solution  being  heated  to  boiling  with  i  c.c.  of  cone,  hydrochloric  acid  and 
5%  barium  chloride  solution  in  slight  excess  added  drop  by  drop  and  with 

1  M.  G.  Levi :  "Methods  of  Analysis  of  Sulphur"  (Ann.  di  chim.  applic.,  1915,  I,  p.  9). 


ii2  SULPHUR 

stirring.    The  precipitate  is  collected  on  a  double  filter,  washed,  dried,  ignited 
and  weighed  as  usual.1    BaS04  X  0-1374  ~  S. 

2.  Crude  Sulphur. 

Crude  sulphur  is  examined  for  the  presence  of  bitumen,  while  the  mois- 
ture and  sulphur  are  detei  mined. 

In  order  to  obtain  a  representative  sample,  each  of  a  number  of  the 
loaves  or  lumps  is  broken  into  6-8  parts  and  from  each  part  a  slice  cut  from 
top  to  bottom,  so  that  the  proportions  of  sulphur,  bitumen  and  extraneous 
substances  are  maintained  in  each  slice.  This  is  of  great  importance  for 
loaves  containing  so-called  oil  or  metal  (veining  or  brown  layers)  or  adul- 
terated with  earthy  matter.  From  5  to  10  kilos  are  taken,  pulverised  and 
passed  through  a  silk  sieve,  the  coarser  particles  being  re-ground  and  again 
sieved  until  the  whole  is  in  fine  powder,  which  is  thoroughly  mixed. 

1.  Bitumen. — A  little  of  the  sample  is  heated  in  a  tube  and  any  car- 
bonaceous residue  noted.     Another  way  is  to  dissolve  the  sample  in  carbon 
disulphide  and  allow  the  filtered  liquid  to  evaporate  spontaneously  in  a 
small  crystallising  dish  :   in  presence  of  bitumen,  a  brownish  or  dark  brown 
border  forms  on  the  walls  of  the  vessel  and  when  all  the  solvent  vanishes, 
crystals  of  sulphur  remain  with  brown  tufts  at  the  salient  points. 

2.  Determination  of  the  Moisture. — 5  grams  of  the  sample  are  heated 
in  a  tared  porcelain  dish  at  100°  in  a  steam- oven  for  1-2  hours  (according  to 
some,  at  70-80°  for  i  hour),  the  loss  representing  moisture. 

3.  Determination  of  the  Sulphur. — The  dried  sulphur  is  next  care 
fully  heated  until  the  sulphur  is  completely  evaporated,  the  loss  then  giving 
the  sulphur.     If  the  sample  contains  bitumen,  the  sulphur  must  be  deter- 
mined by  the  method  described  for  mineral  sulphur. 

These  methods  may  be  applied  directly  to  good  sulphurs  which  leave 
only  traces  of  residue  on  ignition,  but  where  appreciable  mineral  residue 
remains,  the  residue  from  the  carbon  disulphide  extraction  is  employed. 

3.  Refined  Sulphur  (loaves  or  powder) 

In  refined  sulphur  in  loaves  or  powder  (ground,  winnowed)  the  residue 
on  calcination  is  determined  to  check  the  purity.  With  sulphur  ground 
and  sifted  for  agricultural  purposes,  the  degree  of  fineness  must  be  deter- 
mined. 

Determination  of  the  Degree  of  Fineness.- — This  is  effected  by 
Chancel's  so-called  Sulphurimeter  or  Sulphinimeter,  which  consists  of  a 
glass  tube  with  a  ground  stopper  :  the  tube  is  230  mm.  long  and  is  graduated 
from  o  to  100  for  a  space  corresponding  exactly  with  25  c.c.  at  17-5°.  The 

1  To  eliminate  possible  errors  due  to  impurities  in  the  reagents  and  to  allow  for 
the  filter-ash,  a  blank  determination  may  be  carried  out  as  follows  :  25  c.c.  of  the  nitric 
acid  (D  =  1-52)  and  5  drops  of  bromine,  diluted  with  a  little  water,  are  evaporated 
almost  to  dryness  on  a  water-bath,  the  whole  of  the  nitric  acid  being  expelled  by 
evaporating  twice  with  cone,  hydrochloric  acid.  The  residue  is  taken  up  in  water, 
a  little  barium  chloride  added  and  the  liquid  again  evaporated  almost  to  dryness,  filtered 
through  a  double  filter,  the  latter  washed  with  hot  water,  dried,  ashed  and  weighed. 
The  weight  of  this  residue  is  subtracted  from  that  of  the  barium  sulphate  obtained  in 
the  actual  determination  of  the  sulphur. 


SULPHUR  113 

length  of  the  tube  to  the  100  mark  is  175  mm.,  that  of  the  straight  tube  from 
the  10  mark  to  the  100  is  154  mm.,  and  the  bore  of  the  tube  12-68  mm. 

Into  this  tube  are  introduced  5  grams  of  the  sulphur  (which  should  be 
passed  through  a  sieve  of  i  mm.  mesh)  and  about  one-half  of  the  ether  neces- 
sary for  the  determination,  this  being  absolutely  anhydrous  and  alcohol-free, 
D  —  0-719  at  15°.  By  gentle  tapping  the  air  is  completely  displaced,  more 
ether  being  then  added  to  about  i  cm.  beyond  the  100  mark.  The  apparatus 
is  placed  in  a  water-bath  kept  exactly  at  17-5°  ;  after  some  time  the  tube 
is  shaken  vigorously  for  30  seconds  and  returned  to  the  bath,  note  being 
made  of  the  scale-division  reached  by  the  sulphur  suspended  in  the  ethereal 
liquid  :  this  division  represents  the  degree  of  fineness  of  the  sample.  If  the 
temperature  is  2°  above  or  below  17-5°,  the  result  is  raised  or  lowered  by  i 
degree  of  fineness  and  the  necessary  correction  must  be  made. 

The  result  of  the  first  agitation  is  too  high,  so  that  the  determination  is 
repeated  several  times.  After  the  second  or  third  shaking,  the  results 
usually  differ  by  not  more  than  2  and  the  mean  of  two  concordant  results 
is  taken.  Greater  certainty  is  attained  by  carrying  out  the  test  in  duplicate. 

4.  Sublimed  Sulphur  (Flowers  of  Sulphur) 

This  form  of  refined  sulphur  is  in  yellow  powder  composed  mostly  of 
agglomerated,  microscopic  globules  mixed  with  rhombic  crystals  (ground 
sulphur  being  composed  solely  of  crystals  or  crystaUine  fragments).  ,  It  is 
not  completely  soluble  in  carbon  disulphide  (thus  differing  from  ground  sul- 
phur), at  least  12%  and,  in  fresh  samples,  sometimes  more  than  30% 
remaining  undissolved.  When  it  is  moistened  with  water,  the  latter  may 
become  acid  owing  to  the  presence  of  traces  of  sulphuric  acid. 

With  sublimed  sulphur  for  agricultural  purposes,  the  residue  on  cal- 
cination and  the  degree  of  fineness  (see  Refined  Sulphur)  are  determined  ; 
if  for  pharmaceutical  purposes,  arsenic  is  tested  for. 

Detection  of  Arsenic.— 2  grams  are  digested  for  24  hours  with  5  c.c. 
of  10%  ammonia  and  the  solution  filtered,  acidified  with  hydrochloric  acid 
and  saturated  with  hydrogen  sulphide  :  in  presence  of  arsenic  the  liquid 
becomes  yellow. 

5.  Magister  of  Sulphur  (Precipitated  Sulphur) 

Pale  yellow,  almost  colourless,  insipid,  impalpable  powder.  The  tests 
to  be  made  are  :  residue  on  calcination,  which  should  be  inappreciable  ; 
treatment  with  dilute  hydrochloric  acid,  which  should  not  cause  efferves- 
cence, while  the  filtered  liquid  should  not  be  rendered  turbid  by  sodium 
carbonate  (alkaline-earth  carbonates)  ;  digestion  with  water,  which  should 
not  become  acid  ;  test  for  arsenic  (see  Sublimed  Sulphur). 

6.  Coppered  Sulphur 

In  this  product  the  copper  sulphate  is  determined  by  repeatedly  agita- 
ting 10  grams  with  200-250  c.c.  of  hot,  acidified  water,  filtering,  washing 
with  boiling  water  and  estimating  the  copper  by  one  of  the  methods  given 
under  "  Copper  Sulphate." 

A.c,  8 


H4  SULPHUR 

7.  Pyrites 

Pyrites  or  Iron  Pyrites  is  a  natural  ferric  sulphide  containing,  when  pure, 
53'33%  S  and  46-67%  Fe  ;  it  is,  however,  usually  mixed  with  gangue  and 
with  other  minerals,  especially  of  copper,  arsenic,  cobalt,  nickel  and,  not 
infrequently,  silver  and  gold. 

Chalcopyrite  or  Copper  Pyrites  is  a  double  sulphide  of  copper  and  iron, 
containing  in  the  pure  state  34-89%  Cu,  30-54%  Fe  and  34-57%  S  ;  it  is 
often  accompanied  by  iron  pyrites  and  other  minerals. 

The  value  of  pyrites  depends  essentially  on  the  proportions  of  sulphur 
and  copper  (2  and  3,  below).  Other  determinations  usually  made  are 
those  of  moisture,  arsenic  and  lead  (i,  4  and  5). 

1.  Moisture. — 10  grams  of  coarsely  powdered  pyrites  are  kept  in  an 
oven  at  105°  until  of  constant  weight  (4-5  hours  generally  suffice). 

2.  Sulphur  (Lunge's  method). — 0-5  gram  of  pyrites,  finely  powdered 
in  an  agate  mortar  and  sieved  through  a  silk  sieve,  are  treated  with  10  c.c.  of 
a  mixture  of  3  vols.  of  nitric  acid  (D  1-4)  and  I  vol.  of  hydrochloric  acid 
(free  from  sulphuric  acid)  in  a  conical  flask  furnished  with  a  funnel,  this 
being  heated  on  a  water-bath  so  long  as  brown  particles  remain  unattacked 
(if  any  sulphur  is  unacted  on,  a  few  potassium  chlorate  crystals  are  added). 
The  liquid  is  then  transferred  to  a  porcelain  dish — the  flask  and  funnel 
being  well  washed — 'and  evaporated  to  dryness,  the  residue  being  treated 
with  5  c.c.  of  cone.  HC1  and  evaporated  to  dryness  again.     The  residue  is 
then  taken  up  with  i  c.c.  of  cone.  HC1  and  100  c.c.  of  boiling  water,  the 
solution  being  filtered  through  a  small  filter  and  the  latter  well  washed.1 

The  filtrate  is  neutralised  with  ammonia  (D  =  0-91)  and  then  heated 
for  15  minutes  at  60-70°  (not  to  boiling)  with  addition  of  5  c.c.  of  the  same 
ammonia.  The  liquid,  which  should  still  smell  distinctly  of  ammonia, 
is  filtered  at  once  and  the  precipitated  ferric  hydroxide  washed  rapidly  with 
boiling  water  until  the  filtrate  ceases  to  give  turbidity  with  barium  chloride, 
even  after  standing  for  some  minutes.  The  filtrate,  which  should  occupy 
about  300  c.c.,  is  neutralised  with  pure  dilute  hydrochloric  acid  (towards 
methyl  orange),  heated  to  boiling  with  i  c.c.  of  cone,  hydrochloric  acid  and 
precipitated  with  a  boiling  solution  of  barium  chloride  (20  c.c.  of  10%  solu- 
tion usually  suffice).  After  standing,  the  clear  liquid  is  decanted  through 
a  filter,  the  precipitate  washed  3  or  4  times  by  decantation  with  boiling 
water  and  transferred  to  the  filter,  washed,  calcined  and  weighed  :  i  part 
BaSO4  =  0-13734  S. 

3.  Copper  (method  used  att  he  Duisburg  Mines). • — 5  grams  of  extremely 
finely  powdered  pyrites  dried  at  100°  are  treated  in  a  conical  flask  with  60  c.c. 
HNO3  (D  =  1-20).     When  the  action  is  at  an  end,  the  liquid  is  evaporated 
to  dryness  and  the  residue  heated  until  fumes  of  sulphuric  acid  appear,  the 
liquid  being  heated  with  50  c.c.  of  cone.  HC1  and  2  grams  of  sodium  hypo- 
phosphite  dissolved  in  5  c.c.   of  water.     After  addition  of  more  hydro- 
chloric acid  and  dilution  with  about  300  c.c.  of  water,  the  liquid  is  treated 

1  The  insoluble  residue  may  be  dried,  calcined  and  weighed:  it  contains  the  silica, 
silicates,  barium  and  lead  sulphates,  which  may  occur  in  small  amounts  in  pyrites.  If 
the  insoluble  residue^is  very  small  in  quantity,  the  nitration  may  be  omitted. 


SULPHUR  115 

with  hydrogen  sulphide  and  filtered  and  the  precipitated  copper  sulphide, 
with  any  lead,  bismuth  and  antimony  sulphides,  rapidly  washed.  The 
precipitate  is  then  dropped  into  a  conical  flask  and  redissolved  in  nitric 
acid,  with  which  the  filter  is  well  washed.  The  solution  is  evaporated  to 
dryness  and  the  residue  taken  up  in  water  and  a  little  nitric  acid,  neutralised 
with  ammonia,  and  dilute  sulphuric  acid  added  to  precipitate  the  lead.  The 
liquid  is  then  filtered  and  the  insoluble  residue  well  washed,  the  filtrate  being 
treated  with  3-8  c.c.  of  nitric  acid  (D  i'4o)  and  subjected  to  electrolysis  to 
separate  the  copper.  The  weight  of  copper  found  is  diminished  by  o-oi 
gram  to  allow  for  any  bismuth  and  antimony  present. 

Another  method,  more  convenient  and  rapid,  is  as  follows  : 
Five  grams  of  the  very  finely  ground  pyrites  are  carefully  calcined  in  a 
porcelain  dish  at  a  dull  red  heat  and  are  mixed  until  completely  roasted 
(the  arsenic  is  expelled  and  the  tin  rendered  insoluble),  the  product  being 
boiled  for  15  minutes  with  30  c.c.  of  nitric  acid  (D  1-42)  in  a  250  c.c.  flask. 
When  cool,  the  liquid  is  made  up  to  the  mark  with  water,  shaken  and  fil- 
tered, 200  c.c.  of  the  filtrate  (=  4  grams  of  substance)  being  neutralised  with 
ammonia,  mixed  with  5  c.c.  of  cone,  nitric  acid  and  subjected  to  electro- 
lysis (see  Copper  Sulphate,  3,  a). 

With  chalcopyrite  and  products  containing  more  than  15%  Cu,  2  grams 
are  taken  for  analysis. 

4.  Arsenic  (Reich  and  McCay's  method). — 0-5  gram  is  heated  almost 
to  dryness  with  cone,  nitric  acid  in  a  porcelain  basin,  4  grams  of  sodium 
carbonate  being  then  added  and  the  evaporation  continued  to  dryness. 
The  residue  is  then  fused  and  kept  fused  for  10  minutes  with  4  grams  of 
nitre.     When  cold,  the  mass  is  taken  up  in  hot  water  and  the  liquid  filtered, 
acidified  with  nitric  acid,  boiled  to  expel  all  the  carbon  dioxide,  treated 
with  silver  nitrate  and  neutralised  with  dilute  ammonia.     The  precipitate, 
which  contains  all  the  arsenic  as  silver  arsenate,  is  filtered  off,  washed  well 
with  water  and  redissolved  in  dilute  nitric  acid,  the  solution  being  evaporated 
to  dryness  in  a  tared  platinum  basin.     The  residual  silver  arsenate  is  either 
weighed  or  titrated  with  thiocyanate  according  to  Volhard's  method  for 
determining  silver  :    I  part  of  Ag3AsO4  =  0-162  part  of  As  ;    I  part  of  Ag 
=  0-2315  part  of  As. 

5.  Lead. — The  insoluble  residue  remaining  after  the  treatment  with 
aqua  regia  for  the  determination  of  sulphur  (see  2)  is  treated  with  a  hot, 
concentrated  ammonium  acetate  solution,  the  liquid  evaporated  to  dryness 
with  a  little  sulphuric  acid,  and  the  lead  sulphate — thus  separated  from  other 
insoluble  matter — ignited  and  weighed  :   i  part  PbSO4  =  0-6832  part  Pb. 

* 
*   * 

Sicilian  Mineral  sulphur  may  contain  up  to  about  90%  of  sulphur,  but  high 
proportions  (above  40%)  are  rare.  Those  containing  30-40%  are  usually  re- 
garded as  rich,  20-30%  as  good,  15-20%  as  ordinary,  and  less  than  15%  as  poor. 
Most  of  it  is  yellow  tending  to  grey  or  greenish,  but  some  is  brown  owing  to 
bitumen.  Those  of  Romagna  contain,  on  the  average,  10-20%,  and  occasion- 
ally 30%  of  sulphur,  and  are  often  bituminous.  Those  of  Louisiana  are  very 
rich  (60-98%),  while  those  of  Nevada,  Utah,  Texas,  etc.,  contain  varying  pro- 
portions (15-80%). 

Crude  sulphur  usually  contains  98-99-5%  of  sulphur.     The  moisture  rarely 


n6  SULPHUR 

reaches  0-1%  and  the  extraneous  matters  (mineral  substances,  bitumen)  vary 
mostly  from  0-5  to  i%,  but  sometimes  reach  2%. 

Refined  sulphu  and  Sublimed  or  Flowers  of  sulphur  should  contain  only 
negligible  amounts  of  foreign  matter.  Groun  d  and  sifted  sulphur  for  agricultural 
purposes  should  have  a  fineness  superior  to  50  degrees  on  Chancel's  sulphurimeter. 

Washed  flowers  of  sulphur  and  Milk  (Magister)  of  s^tlph^^r,  for  pharmaceutical 
uses,  should,  according  to  the  official  Italian  Pharmacopoeia,  be  free  from  arsenic 
and  other  impurities,  and  should  leave  not  more  than  i  %  (flowers)  or  an  inappre- 
ciable amount  (milk)  of  residue  when  burnt. 

Iron  pyrites  mostly  contain  40-50  %  of  sulphur. 


CHAPTER  III 
FERTILISERS 

Fertilisers  include  many  substances  of  organic  or  mineral  origin,  their 
active  constituents  being  : 

Nitrogen,  in  the  form  of  organic  or  insoluble  nitrogen,  as  it  occurs  in  dried 
blood,  meat  guano,  wool  waste,  horns,  nails,  leather,  etc.,  bone  meal,  dung, 
guano,  excrements,  etc.  Nitric  nitrogen,  occurring  mostly  in  sodium  and 
potassium  nitrates.  A  mmoniacal  nitrogen,  in  ammonium  sulphate. 

Potash,  given  especially  by  potassium  nitrate,  sulphate  and  chloride, 
kainit,  carnallite,  etc. 

Phosphoric  acid,  which  may  occur  in  the  insoluble  state  (tricalcic  phos- 
phate), as  in  natural  phosphates  (phosphorites,  apatites  and  coprolites), 
bone  ash,  degelatinised  bones,  bone  black,  guano  and  other  animal  ferti- 
lisers ;  in  a  condition  soluble  in  ammonium  citrate  (dicalcium  phosphate), 
as  in  precipitated  phosphates  and  dephosphorisation  slags  ;  in  a  condition 
soluble  in  water  (monocalcium  phosphate),  as  in  the  superphosphates. 

Analysis  of  fertilisers  in  general  comprises  essentially  determinations  of 
the  moisture,  nitrogen,  phosphoric  acid  (in  its  various  forms)  and  potash. 
These  determinations  are  described  among  the  general  methods  of  analysis 
(see  p.  118).  Other  determinations  to  be  made  with  special  fertilisers  are 
given  in  the  separate  cases. 

Of  special  importance  in  these  analyses  is  the  taking  of  the  samples  and 
their  preparation  in  the  laboratory,  the  procedure  to  be  followed  being  as 
described  below. 

1.  Taking  and  Despatch  of  Samples. — With  homogeneous  powdered 
fertilisers  (phosphates,  bone  ash,  sodium  nitrate,  ammonium  sulphate,  potash 
fertilisers),  several  samples  of  200-300  grams  are  taken  either  from  various 
points  and  different  heights  of  the  mass  if  this  is  in  heaps,  or  from  different 
sacks.  From  these  samples,  which  are  more  or  less  numerous  according 
to  the  magnitude  of  the  parcel,  a  single  heap  (about  3-5  kilos)  is  made. 
This  is  thoroughly  mixed  and  any  lumps  broken  to  make  it  homogeneous, 
the  sample  for  analysis  being  then  taken. 

If  the  fertiliser  is  mixed,  that  is,  prepared  from  powdered  products  mixed 
according  to  definite  formulae,  a  larger  number  of  samples  are  taken  and 
mixed,  portions  from  different  parts  of  this  being  thoroughly  mixed  and 
the  sample  for  analysis  taken  from  this  heap. 

With  pasty  fertilisers,  a  number  of  shovelfuls  are  taken  and  mixed  well, 
all  lumps  being  broken  down  ;  the  sample  for  analysis  is  then  taken. 

With  non-homogeneous  and  non-pidverulent  fertilisers  (bones,  dried  meat 

117 


u8  FERTILISERS 

and  blood,  nails,  hair,  horns  and  the  like),  a  number  of  handfuls  are  taken 
from  different  parts  of  the  mass  and  mixed  as  well  as  possible  before  the 
sample  is  taken. 

Liquid  fertilisers  or  liquids  with  suspended  or  deposited  matter  are  well 
mixed  with  a  stick. 

The  samples  for  analysis  should  be  in  three  lots  of  at  least  300  grams 
each  for  powdered  fertilisers  or  i  kilo  in  other  cases. 

Powdered  or  pasty  samples  are  placed  in  glass  vessels  with  ground  stop- 
pers or  tight  corks,  non-pulverulent  samples  in  new  bags  or  wooden  boxes 
and  liquids  in  well  cleaned  bottles  with  new  stoppers. 

Each  sample,  duly  sealed  with  sealing-wax,  should  bear  a  label  indicating 
the  quality  of  the  product,  the  quantity  from  which  it  wras  taken,  the  origin 
and  the  date  of  sampling  ;  to  this  should  be  added  a  declaration  of  the  sender 
indicating  the  nature  of  the  material  sent  or  that  for  which  it  has  been  sold, 
the  strength  (%  of  phosphoric  anhydride,  nitrogen,  potash)  guaranteed,  and 
the  determinations  required. 

2.  Preparation  of  the  Sample  in  the  Laboratory. — Before  analysis, 
the  whole  of  the  sample  should  be  re-mixed  and  powdered  to  render  it 
homogeneous.  If,  however,  the  degree  of  fineness  is  to  be  determined,  the 
sample  is  mixed  with  a  spatula  and  the  portion  necessary  for  such  test  set 
aside,  the  rest  being  ground  in  a  mortar. 

If  the  fertiliser  contains  hard  lumps  or  pieces  mixed  with  powder,  it  is 
sieved  through  a  0-5-1  mm.  sieve,  the  part  remaining  in  the  sieve  being 
powdered  and  re-sieved  so  as  to  obtain  a  uniform  powder,  which  is  finally 
thoroughly  mixed. 

Bones  in  lumps  are  broken  in  a  mill  or  mortar  and,  if  possible,  powdered  ; 
if  not  they  are  first  dried  at  a  low  temperature  (allowance  being  made  for 
the  moisture  lost). 

Waste  wool,  hair,  leather,  and  the  like  are  finely  cut  with  scissors  and 
then  mixed.  Horns  and  nails  may  be  powdered  in  an  ordinary  mill. 

Stable  manure  and  very  wet  or  pasty  fertilisers  are  dried  at  a  low  tem- 
perature and  then  mixed  and  powdered,  account  being  taken  of  the  moisture 
lost  (see  General  Methods,  2,  and  Stable  Manure). 

GENERAL    METHODS 

These  methods  treat  of  certain  preliminary  tests  and  determinations 
generally  applicable,  except  where  indicated,  to  the  different  types  of 
fertilisers. 

1.  Preliminary  Tests 

When  the  nature  of  a  fertiliser  is  not  definitely  known,  the  following 
tests  are  made  in  order  to  regulate  the  subsequent  determinations : 

1.  Reaction. — 5  grams  are  mixed  with  4-5   c.c.   of  water,  and  the 
reaction  of  the  liquid  tested  with  litmus  paper. 

2.  Nitrogen. 

(a)  Ammoniacal  Nitrogen.  About  I  gram  of  the  fertiliser  is  boiled  with 
5  c.c.  of  water  and  about  0-25  gram  of  calcined  magnesia  :  evolution  of 
ammonia  indicates  the  presence  of  ammoniacal  nitrogen. 


FERTILISERS   (GENERAL  METHODS)  119 

(b)  Nitric  Nitrogen.     I  gram  of  the  fertiliser  is  treated  with  2  c.c.  of 
water,  the  liquid  filtered  and  the  filtrate  tested  with  cone,  sulphuric  acid 
and  ferrous  sulphate  in  the  usual  way. 

(c)  Organic  Nitrogen.     In  absence  of  ammonia,  0-5  gram  of  the  fertiliser 
is  heated  with  soda  lime  :  evolution  of  ammonia  indicates  organic  nitrogen. 
If  ammoniacal  salts  are  present,  these  must  be  removed  by  extraction  with 
water  and  then  dried,  the  insoluble  residue  being  tested  with  soda  lime. 

3.  Phosphoric  Acid. 

(a)  Phosphoric  Acid  soluble  in  Water.    Half  a  gram  is  mixed  with  4-5  c.c. 
of  .water  and  left  to  stand,  a  little  of  the  clear  liquid  being  pipetted  off  subse- 
quently and  tested  with  ammonium  molybdate. 

(b)  Soluble  in  Ammonium  Citrate  (Retrograde  or  reverted  phosphate).     A 
few  grams  are  extracted  several  times  with  water  and  the  residual  insoluble 
matter  digested  with  about  20  c.c.  of  ammonium  citrate  solution  (for  its 
preparation,  see  p.  123)  ;   the  liquid  is  filtered  and  the  filtrate  tested  with 
magnesia  mixture. 

(c)  Insoluble.     The  residue  insoluble  in  ammonium  citrate  is  washed 
several  times  with  ammonium  citrate  solution  boiled  with  7-8  c.c.  of  nitric 
acid  and  allowed  to  stand,  a  little  of  the  clear  liquid  being  subsequently 
tested  with  ammonium  molybdate. 

4.  Potash. 

(a)  SohMe  in  Water.     About  2  grams  are  boiled  with  10  c.c.  of  water 
and  the  liquid  filtered. 

To  one  portion  of  the  filtrate  an  equal  volume  of  10%  sodium  thiosul- 
phate  solution  is  added  and  then  3-4  drops  of  Carnot's  reagent  x  and  double 
the  volume  of  95%  alcohol :  in  presence  of  potash  a  yellow  crystalline  pre- 
cipitate is  formed. 

The  other  portion  is  rendered  faintly  alkaline  with  sodium  hydroxide, 
filtered  and  acidified  slightly  with  hydrochloric  acid.  Addition  of  I  c.c.  of 
perchloric  acid  (D  =  1-12)  and  an  equal  volume  of  alcohol  yields  a  white 
precipitate  in  presence  of  potash. 

(b)  Insoluble  in  Water.    Two  grams  are  thoroughly  exhausted  with  hot 
water  and  the  undissolved  part  boiled  with  a  mixture  of  5  c.c.  of  cone, 
nitric  acid  and  10  c.c.  of  cone,  hydrochloric  acid,  the  liquid  being  diluted, 
filtered,  evaporated  to  dryness  and  the  residue  redissolved  in  water  ;    this 
solution  is  then  tested  as  in  the  preceding  case. 

2.  Determination  of  the  Moisture 

From  5  to  10  grams  are  heated  at  100°  to  constant  weight.  Superphos- 
phates and  other  products  rich  in  gypsum  are  dried  in  a  boiling  water-oven 
for  4  hours. 

If  the  fertiliser  has  an  alkaline  reaction  or  it  is  feared  that  ammonia 
may  be  lost  during  the  drying,  as,  for  instance,  with  stable  manure,  the 
fertiliser  (5  grams)  is  placed  in  a  tared  porcelain  boat  and  this  introduced 
into  a  glass  tube  arranged  in  a  suitable  oven.  One  end  of  the  tube  is  con- 

1  ioo  grams  of  basic  bismuth  nitrate  (magister  of  bismuth)  are  dissolved  in  the  hot 
in  cone,  hydrochloric  acid  and  diluted  to  a  litre  with  92%  alcohol. 


120 


FERTILISERS   (GENERAL  METHODS) 


nected  with  a  wash-bottle  containing  cone,  sulphuric  acid  and  the  other 
with  a  bulb-tube  charged  with  20  or  25  c.c.  N/io-sulphuric  acid.  The  oven 
is  heated  at  100°  and  during  the  drying  a  slow  current  of  air  is  passed  through 
the  glass  tube.  The  boat  is  finally  reweighed  and  the  loss  of  weight  dimin- 
ished by  the  weight  of  ammonium  carbonate  corresponding  with  the  ammonia 
absorbed  by  N/io-sulphuric  acid. 

If  the  fertiliser  has  an  acid  reaction  and  it  is  feared  that  loss  of  volatile 
acid  or  changes  rendering  the  estimation  inaccurate  will  occur  in  drying, 
the  fertiliser  is  first  neutralised.  To  this  end  5  grams  are  weighed  in  a 
weighing  bottle,  tared  together  with  a  thin  glass  rod.  The  mass  is  then 
moistened  and  neutralised  with  N-caustic  soda  solution.  That  neutralisa- 
tion is  approaching  is  indicated  by  the  ready  clarification  of  the  supernatant 
liquid  and  the  exact  point  determined  by  touching  litmus  paper  with  the 
rod.  The  liquid  is  then  evaporated  to  dryness  and  the  crust  broken  with 
the  rod,  drying  being  then  continued  for  a  further  period  of  4  hours.  Each 
c.c.  of  N-caustic  soda  added  increases  the  weight  of  the  dry  matter  by  0-022 
gram. 

3.  Determination  of  the  Nitrogen 

The  nitrogen  is  determined  in  different  ways  according  to  its  condition. 
A.  Ammoniacal  Nitrogen. — 5-10  grams  of  the  substance  are  mixed 
with  water  (acidified  in  the  case  of  an  alkaline  reaction)  in  a  mortar,  the 
liquid  being  decanted  into  a  250  c.c.  or  500  c.c.  flask.  The  insoluble  matter 
is  washed  by  decantation  and  the  total  liquid  made  up  to  volume  and  the 
ammonia  in  an  aliquot  part  found  by  distillation  with  excess  of  sodium 

hydroxide  (or  calcined  magnesia,  in  case 
organic  nitrogen  readily  decomposable  by 
alkali  is  present).  The  apparatus  and  pro- 
cedure are  described  under  Kjeldahl  method 
(see  later,  C). 

B.    Nitric    Nitrogen.      This    may    be 
determined  by  the  two  following  methods  : 

I.    SCHULZE     AND     TlEMANN'S     METHOD. 

To  a  flask  a  of  150-200  c.c.  capacity  (see 
Fig.  2)  is  fitted  a  doubly-bored  stopper 
traversed  by  two  capillary  tubes,  one  of 
which  serves  for  the  delivery  of  the  nitric 
oxide  into  the  graduated  tube  I  standing 
over  water,  while  the  other,  slightly  con- 
stricted at  the  end,  dips  into  a  conical  beaker  i  ;  in  each  tube  is  inserted  a 
piece  of  pressure  rubber  tubing  5  cm.  long  fitted  with  a  screw  clip,  /,  g. 

The  flask  is  charged  with  20  c.c.  of  1-65  %  pure  sodium  nitrate  solution 
(or  20  c.c.  of  2-0%  potassium  nitrate  solution)  when  the  fertiliser  contains 
sodium  (or  potassium)  nitrate,  and  about  30  c.c.  of  water.  The  stopper 
is  inserted  and,  the  two  clips  being  open,  the  liquid  boiled  to  expel  all  air 
from  the  flask  and  the  capillary  tubes.  When  the  liquid  is  reduced  to  a 
small  volume  (about  15  c.c.),  the  delivery  tube  for  the  nitric  oxide  is  dipped 
into  a  boiled  10%  caustic  soda  solution  and  the  clip  closed.  If  the  air  has 


FIG.  2 


FERTILISERS   (GENERAL  METHODS)  121 

been  completely  removed,  the  soda  solution  will  fill  the  part  of  the  tube 
below  the  clip  immediately  and  completely.  Shortly  after,  when  a  little 
water  has  condensed  in  the  conical  beaker  so  as  to  cover  the  extremity 
of  the  other  capillary  tube,  the  second  clip  is  shut  and  the  flame  at  once 
removed  from  beneath  the  flask. 

About  15-20  c.c.  of  ferrous  chloride  solution  are  1  poured  into  the  beaker 
and  allowed  to  pass  into  the  flask  by  opening  the  clip.  When  the  ferrous 
solution  only  just  covers  the  tip  of  the  capillary  tube,  a  little  hydrochloric 
acid  (D  i-i)  is  poured  into  the  beaker  and  later  a  little  more,  so  as  to  wash 
out  the  beaker  and  displace  all  the  ferrous  chloride  from  the  tube,  care  being 
taken  that  no  air  enters  the  tube  and  hence  the  flask  a  ;  about  10  c.c.  of 
acid  is  sufficient  for  this  purpose.  The  clip  is  closed,  the  flame  replaced 
under  the  flask  and  a  graduated  tube  (100  c.c.  reading  to  0-5  c.c.)  filled 
with  boiled  10%  caustic  soda  solution  placed  over  the  end  of  the  gas  delivery 
tube.  When  the  rubber  joint  of  this  tube  begins  to  swell,  the  clip  is  replaced 
by  the  fingers,  and  as  soon  as  evolution  of  nitric  oxide  begins,  the  joint  is 
left  free.  The  boiling  is  regulated  so  that  liberation  of  gas  is  not  too  rapid, 
and  when  this  ceases  the  graduated  tube  is  closed  by  the  thumb  and  shaken 
and  then  placed  in  a  bath  of  water. 

The  flask  is  then  rinsed  out  and  the  operation  repeated  in  identical  man- 
ner with  the  solution  of  the  substance  to  be  tested.  With  sodium  (or  potas- 
sium) nitrate  or  fertiliser  containing  it,  16*5  (or  20)  grams  are  dissolved  in 
hot  water  and,  if  insoluble  residue  remains,  filtered  and  the  residue  washed  ; 
the  volume  is  then  made  up  to  I  litre.2  Of  this  solution  20  c.c.  are  introduced 
into  flask  a  if  the  nitrate  alone  is  being  tested  or  double  or  three  times,  etc., 
as  much  in  the  case  of  mixed  fertilisers,  so  that  the  volume  of  NO  collected 
is  about  the  same  as  in  the  control  experiment  with  the  pure  nitrate. 

The  second  tube  containing  nitric  oxide  is  placed  in  the  same  bath  of 
water  as  the  first  and  when  the  temperature  of  the  gas  is  in  equilibrium  with 
that  of  the  surrounding  air  (about  i  hour  is  sufficient),  the  two  tubes  are 
immersed  in  the  bath  so  that  the  levels  inside  and  outside  are  the  same. 
The  volume  of  the  gas  is  then  read  off  in  each  case  at  the  lower  edge  of  the 
meniscus. 

When  equal  quantities  of  the  fertiliser  and  pure  nitrate  are  used,  the 
percentage  (x)  of  nitrogen  is  given  by  the  formula 

K(a  x  100) 

/Y    — —  v ' 

~b~ 

where  K  —  the  coefficient  for  reducing  the  nitrate  to  nitrogen  and  has  the 

value  0-1647  for  NaNO3  and  0-1387  for  KN03, 
a  =  c.c.  of  NO  obtained  from  the  fertiliser. 
b  =  c.c.  of  NO  obtained  from  the  pure  nitrate. 

1  This  solution  is  prepared  by  placing  200  grams  of  fine  iron  filings  in  a  flask  with 
100  c.c.  of  water,  and  gradually  heating  the  flask  on  a  sand-bath  and  adding  hydro- 
chloric acid  (D  i -i)  until  all  the  iron  is  dissolved.     The  liquid  is  filtered  to   get  rid  of 
carbon  and  made  up  to   i   litre  with  boiled  water. 

2  If  the  fertiliser  contains  carbonate,  the  solution  is  prepared  with  water  containing 
hydrochloric  acid  to  eliminate  the  carbon  dioxide.     If  the  fertiliser  contains  oxalic  acid 
(guano),  the  latter  is  rendered  insoluble  by  addition  of  a  little  milk  of  lime. 


122  FERTILISERS   (GENERAL  METHODS) 

The  percentage  (x)  of  NaNO3  or  KNO3  may  be  calculated  by  the  formula, 

a  x  100 


2.  JODLBAUR'S  MODIFIED  KJELDAHL  METHOD.  This  is  applied  in  the 
manner  indicated  under  D  for  the  total  nitrogen.  With  nitrates  0-5  gram 
is  taken,  and  with  mixed  fertilisers  i  gram.  N  x  0-1647  =  NaNO3 ; 
N  x  0-1387  =  KNO3. 

The  result  obtained  by  this  method  must,  of  course,  be  diminished  by 
the  porportions  of  ammoniacal  and  organic  nitrogen  (found  under  A  and 
C)  present. 

C.  Organic  Nitrogen. — This  is  determined  by  Ulsch's  modification 
of  the  Kjeldahl  method  : 

Into  a  long-necked,  pear-shaped  flask  of  good  resistant  glass  holding 

about  250  c.c.1  from  i  to  5  grams 
(according  to  the  nitrogen  content) 
of  the  substance  arc  introduced,2 
together  with  20-25  c-c-  of  phos- 
phosulphuric  acid  (125  grams  of 
phosphoric  anhydride  dissolved  in 
i  litre  of  sulphuric  acid  of  66° 
Baume),  2-3  drops  of  10%  platinum 
chloride  solution,  and  0-2-0-3  gram 
of  copper  oxide. 

The  flask  is  closed  with  a  small 
funnel  or,  better,  with  a  light  glass 
bulb  drawn  out  to  a  point  at  one 
end,  and  is  then  placed  sloping  on 
an  asbestos-covered  gauze  and 
heated,  at  first  with  a  small  flame 
and  then  to  boiling  until  a  clear  and 
almost,  if  not  quite,  colourless  solu- 
tion is  obtained.  In  this  way  the 
organic  nitrogen  is  wholly  converted 
into  ammonium  sulphate. 

When  cold,  the  liquid  is  carefully 
diluted  with  water  and  washed  out 
into  a  flask  of  about  i  litre  capacity. 
The  liquid  is  then  rendered  alkaline 


FIG.  3 


with  excess  of  sodium  hydroxide 
solution  (about  30%)  and  the  am- 
monia distilled,  an  apparatus  similar  to  that  shown  in  Fig.  3  being  used. 
The  flask  A  contains  the  alkaline  liquid  to  be  distilled,  the  bulb  B  serves  to 
retain  any  alkali  spurting  over  and  is  formed  of  two  concentric  glass  bulbs,  the 

1  Suitable  flasks  and  other  accessories  for  the  Kjeldahl  method  are  sold. 

2  With  liquids,  such  volume  or  weight  is  taken  as  corresponds  with  1-5  grams  of 
solid  substance,  according  to  the  nitrogen  content.     The  liquid  is  then  evaporated  to 
dryness  in  the  Kjeldahl  flask  itself. 


FERTILISERS   (GENERAL  METHODS)  123 

inner  one  with  two  lateral  orifices  ;  the  conical  flask  C  contains  20-25  c-c- 
(exact  amount)  of  N/2-sulphuric  acid  and  the  safety  tube  D  a  little  water. 

When  200-250  c.c.  of  liquid  have  distilled  over,  the  flask  C  and  tube  D 
are  detached,  the  latter  being  washed  into  the  flask  and  the  contents  of  the 
latter  titrated  with  N/2-sodium  hydroxide  in  presence  of  methyl  orange. 
The  number  of  c.c.  of  N/2-acid  neutralised,  multiplied  by  0-007,  gives  the 
amount  of  nitrogen  in  grams  in  the  weight  of  substance  taken  for  analysis. 
In  cases  where  ammoniacal  nitrogen  is  present  as  well  as  organic  nitrogen, 
the  result  just  obtained  must  be  diminished  by  that  obtained  by  method  (A). 

D.  Total  Nitrogen. — The  preceding  methods  give  the  total  nitrogen 
where  this  is  all  of  one  form  or  a  mixture  of  ammoniacal  and  organic.  If, 
besides  these  two,  nitric  nitrogen  is  also  present,  the  total  nitrogen  is  deter- 
mined as  follows  : 

Jodlbaur's  modification  of  the  Kjeldahl  method.  From  i  to  5  grams  of 
substance  l  are  well  mixed  in  a  Kjeldahl  flask  with  20  c.c.  of  phenol-sulphuric 
acid  solution  (40  grams  of  phenol  dissolved  in  I  litre  of  sulphuric  acid  of 
66°  Baume)  and,  after  5  minutes,  2-3  grams  of  zinc  dust  are  added  in  small 
portions  and  with  cooling.  The  flask  is  then  heated  over  a  small  flame  for 
10-15  minutes,  allowed  to  cool  and  5  c.c.  of  phosphosulphuric  acid  (see  under 
C),  a  little  copper  oxide  and  a  few  drops  of  platinic  chloride  solution  added, 
the  subsequent  procedure  being  as  in  the  Ulsch  method  (see  under  C). 

The  official  Italian  methods  conform  to  those  given  above,  but  they  allow 
also  :  (i)  for  nitric  nitrogen,  of  the  use  of  Ulsch's  method,  which  consists  in 
reduction  of  nitrates  to  ammonia  by  means  of  reduced  iron  or  zinc,  and  of 
Devarda's  method,  in  which  the  reduction  is  effected  by  aluminium  or  zinc  in 
alkaline  solution  ;  (2)  for  the  total  nitrogen  of  the  use  of  Dumas'  method. 

4.  Determination  of  the  Phosphoric  Acid 

Determinations  may  be  required  of  the  total  phosphoric  acid,  of  that 
soluble  in  water,  and  of  that  soluble  in  ammonium  citrate.  Here  is  described 
only  the  method  for  the  total  phosphoric  acid,  applicable  to  all  phosphatic 
fertilisers  except  Thomas  slag  (q.v.).  Estimation  of  the  phosphoric  acid 
soluble  in  water  or  in  citrate,  applicable  essentially  to  superphosphates  and 
other  slags,  is  treated  later  in  dealing  with  these  products  in  particular. 

Determination  of  the  Total  Phosphoric  Acid. — The  following  solu- 
tions are  required  : 

(a)  A mmonium  citrate.     400  grams  of  crystallised  citric  acid  are  covered 
with  water  and  neutralised  with    ammonia   (D  =  0-92)    (about    500    c.c. 
required),  the  liquid  being  cooled  meanwhile  and  finally  made  up  to  i  litre. 

(b)  Magnesia  Mixture,     no  grams  of  crystallised  magnesium  chloride, 
140  grams  of  ammonium  chloride,  700  c.c.  of  8%  ammonia  (D  =  0-967) 
and  1300  c.c.  of  water. 

(c)  Ammonia,  D  =0-920. 

PROCEDURE.  Five  grams  of  the  substance  are  boiled  for  about  30 
minutes  in  a  250  c.c.  measuring  flask  with  50-75  c.c.  of  water,  20  c.c.  of 

1  If  this  is  moist  or  difficult  to  attack,  it  is  well  to  add  2-3  grams  of  finely  powdered 
burnt  gypsum. 


124  FERTILISERS   (GENERAL  METHODS) 

hydrochloric  acid  and  5  c.c.  of  cone,  nitric  acid,  and  subsequently  diluted 
with  water,  allowed  to  cool,  made  up  to  volume  and  filtered. 

To  25  c.c.  of  the  filtrate  (=  0-5  gram  of  substance),  or  50  c.c.  (=  i  gram) 
with  a  poor  phosphate,  are  added  20  c.c.  of  the  ammonium  citrate,  50  c.c.  of 
water,  50  c.c.  of  ammonia  (D  0-92)  and  50  c.c.  of  magnesia  mixture,  the 
whole  being  then  stirred  vigorously  without  the  stirrer  touching  the  walls 
of  the  vessel.  After  being  stirred  continuously  for  30  minutes  with  a  mechan- 
ical stirrer  or,  if  this  is  not  available,  after  standing  for  at  least  5-6  hours, 
the  liquid  is  filtered  and  the  precipitate  washed,  first  by  decantation  and 
then  on  the  filter  with  ammonia  (i  vol.  of  ammonia  of  D  =  0-96  and  3 
vols.  of  water)  until  the  wash  liquor  is  free  from  chloride.  The  filter  is  then 
dried  at  100°,  the  precipitate  detached,  the  filter-paper  burnt  separately  and 
precipitate  and  filter-ash  heated  together  in  a  platinum  crucible  until  of 
constant  weight.  The  weight  of  magnesium  pyrophosphate  thus  obtained, 
multiplied  by  128  when  0-5  gram  of  substance  was  taken  or  by  64  for  i 
gram,  gives  directly  the  amount  of  phosphoric  anhydride  (P2O5)  per  100 
grams  of  substance,  the  results  being  always  expressed  in  this  form. 

Menozzi's  modification  (1898)  of  Pemberton's  volumetric  method  is  also 
included  among  the  Italian  official  methods. 


5.  Determination  of  the  Potash 

From  5  to  10  grams  of  substance  •"•  are  heated  to  boiling  with  200-250 
c.c.  of  water  and  5-10  c.c.  of  cone,  hydrochloric  acid  in  a  500  c.c.  measuring 
flask.  When  cool,  the  liquid  is  made  up  to  volume  and  mixed,  100  c.c.  of 
the  solution  (1-2  grams  of  substance)  being  then  transferred  to  another 
500  c.c.  flask  and  boiled.  At  this  point,  if  the  material  is  rich  in  sulphate, 
barium  chloride  solution  is  added  until  no  further  precipitation  occurs  and 
then  slight  excess  of  baryta  water  (phenolphthalein  being  added  to  the  liquid, 
the  baryta  is  added  until  the  solution  turns  red)  ;  if  the  material  is  poor  in, 
or  free  from,  sulphate,  baryta  solution  alone  is  added.  When  cold,  the 
liquid  is  made  up  to  volume,  shaken,  and  filtered  through  a  dry  filter,  250  c.c. 
of  the  filtrate  (0-5-1  gram  of  substance)  being  introduced  into  another  500 
c.c.  flask  and  boiled.  Ammonium  carbonate  solution  is  then  gradually 
added,  with  constant  agitation,  as  long  as  precipitate  is  formed,  the  flask 
being  heated  for  some  time  on  a  steam-bath  in  order  that  the  precipitated 
barium  carbonate  may  become  crystalline.  When  cold,  the  volume  is  made 
up  and  the  liquid  shaken  and  filtered.2 

1  With  complex  organic  fertilisers,  10-20  grams  (according  to  the  supposed  richness 
in  potash)  are  charred  in  a  platinum  dish  at  a  red  heat,  the  mass  being  extracted  with 
water  and  cone,  hydrochloric  acid  and  the  liquid  evaporated  to  dryness.    The  residue 
is  heated  at  120°,  dissolved  in  dilute  hydrochloric  acid,  transferred  to  a  500  c.c.  flask, 
made  up  to  volume  and  mixed.     An  aliquot  part  of  the  liquid  is  then  treated  with 
barium  chloride,  baryta,  etc.,  in  the  ordinary  way. 

2  With  potassium  chloride  or  sulphate,  the  treatment  with  barium  chloride,  baryta 
water  and  ammonium  carbonate  may  be  made  successively  in  the  original  flask  in 
which  the  substance  (5  grams)  is  dissolved,  the  volume  being  then  made  up  and  the 
liquid  shaken  and  filtered,  25  c.c.  of  the  nitrate  (=  0-25  gram  of  substance)  being  then 
taken.     At  this  dilution  the  volume  occupied  by  the  precipitate  is  without  appreciable 
influence. 


AMMONIUM  SULPHATE  125 

Of  the  filtrate,  250  c.c.  are  evaporated  to  dryness,  gently  ignited  to  expel 
the  ammonium  salts,  the  residue  being  dissolved  in  hot  water  and  the  solu- 
tion filtered  through  a  small  filter,  which  is  well  washed  with  hot  water. 
The  liquid  is  evaporated  to  a  small  volume  (about  10  c.c.)  in  a  porcelain  or 
glass  dish  on  a  steam-bath  and  the  potassium  determined  by  one  of  the 
following  methods  : 

(a)  PLATINUM  CHLORIDE  METHOD.  The  small  quantity  of  liquid  is 
evaporated  to  a  syrup  with  25  c.c.  of  10%  platinum  chloride  solution,  being 
frequently  'stirred  with  a  glass  rod  ;  50  c.c.  of  alcohol  (85-5%  by 
volume  =  80%  by  weight)  are  then  stirred  in  and  after  an  hour  the  liquid 
filtered  through  a  filter  dried  at  100°  and  tared,  the  precipitate  being  well 
washed  with  alcohol  of  the  above  strength,  dried  at  100°  and  weighed.1 
K2PtCl6  x  0-194  =  K2O. 

(&)  PERCHLORATE  METHOD.  The  concentrated  solution,  in  a  glass 
dish,  is  evaporated  on  a  water-bath  with  about  15  c.c.  of  perchloric  acid  of 
D  1-12  (about  20%)  until  the  hydrochloric  acid  is  completely  expelled  and 
white  fumes  of  perchloric  acid  appear.  On  cooling,  the  residue  is  mixed 
with  25  c.c.  of  approximately  95%  alcohol  containing  0-2%  of  perchloric 
acid,  all  lumps  being  broken  up  with  a  glass  rod.  After  the  lapse  of  30 
minutes,  the  precipitate  is  collected  on  a  Gooch  crucible  previously  dried 
at  120°  and  weighed,  washed  with  not  more  than  70-75  c.c.  of  95%  alcohol 
containing  0-2%  of  perchloric  acid  and  finally  with  pure  95%  alcohol.  It 
is  then  dried  at  120°  and  weighed.  The  content  of  potash  is  expressed  as 
percentage  of  K20. 


SPECIAL   PART 
Nitrogenous  Fertilisers 

AMMONIUM    SULPHATE 

A  crystalline  powder,  greyish  or  sometimes  reddish,  yellowish  or  bluish 
according  to  the  impurities  it  contains  ;  the  pure  salt  is  colourless. 
The  determinations  and  tests  to  be  made  are  as  follows  : 

1.  Moisture. — 5  grams  are  heated  at  110-120°  to  constant  weight. 

2.  Nitrogen. — 10  grams  are  dissolved  in  water  to  I  litre  and  50  c.c. 
of  this  solution  (=  0-5  gram  of  substance)  distilled  with  sodium  hydroxide 
(see  General  Methods,  3,  A). 

3.  Fixed  Residue. — 3  grams  are  ignited  until  no  further  evolution  of 
volatile  matters  takes  place. 

4.  Thiocyanates. — 2  grams  are  dissolved  in  20  c.c.  of  water  and  a  little 
hydrochloric  acid  and  ferric  chloride  added  :    in  presence  of  thiocyanates 
a  red  coloration  forms. 

1  Instead  of  a  filter-paper  a  Gooch  crucible  may  be  used.  The  precipitate  is  col- 
lected in  this,  dried  at  100°  and  weighed.  The  crucible  is  then  washed  with  boiling 
water  to  dissolve  the  precipitate,  again  dried  and  weighed.  The  loss  in  weight  gives  the 
potassium  platinichloride. 


126  SODIUM  NITRATE   (CHILI   SALTPETRE) 

5.  Free  Sulphuric  Acid. — A  solution  of  20  grams  in  water  is  titrated 
with  N/2-sodium  hydroxide  in  presence  of  methyl  orange. 


* 
*  * 


Pure  ammonium  sulphate  contains  21-21%  N  and  should  leave  no  residue  on 
ignition.  The  commercial  salt  should  contain  at  least  19%  N,  but  usually  con- 
tains 20-21%. 

SODIUM    NITRATE  (Chili  Saltpetre) 

Minute  grey  or  yellowish  crystals  containing,  as  impurities,  chlorides, 
sulphates,  insoluble  substances  and  perchlorates.  The  more  important 
tests  and  determinations  are  as  follows  : 

1.  Moisture. — 5  grams  are  heated  in  an  oven  at  110-120°  to  constant 
weight.     The  nitrate  may  also  be  weighed  in  a  crucible,  heated  carefully 
to  incipient  fusion,  allowed  to  cool  in  a  desiccator  and  re- weighed. 

2.  Various  Impurities.— The  insoluble  matter,  chlorides,  sulphates, 
lime,  etc.,  are  detected  and,  where  necessary,  estimated  by  the  ordinary 
analytical  methods. 

3.  Detection  of  Perchlorates. — 10-20  grams  are  dissolved  in  as  much 
water  and  filtered,  a  few  drops  of  the  filtrate  being  treated  on  a  microscope 
slide  with  1-2  crystals  of  rubidium  chloride  and  the  liquid  coloured  pink 
with  one  or  two  drops  of  dilute  potassium  permanganate  solution.     After 
careful  evaporation  over  a  very  small  flame  until  a  crust  forms  at  the  edges  of 
the  liquid,  a  cover-slip  is  placed  on  the  drop  and  the  latter  examined  under 
the  microscope  :    the  presence  of  perchlorate  is  indicated  by  dark  violet- 
red,  rhombic  crystals  of   rubidium  perchlorate,  often  in  stellate  groupings, 
by  the  side  of  the  colourless  sodium  nitrate  crystals. 

4.  Determination    of   Perchlorate. — This   may    be    carried    out    as 
follows  : 

The  chlorine  in  the  nitrate  is  first  determined  by  one  of  the  ordinary 
methods.  Another  portion  of  5  or  10  grams  of  the  finely  powdered  nitrate 
is  mixed  witli  pure  calcium  oxide  (8  grams)  or  carbonate  (15  grams)  (quite 
free  from  chlorine)  and  the  mixture  heated  for  about  15  minutes  in  a  plali 
num  or  porcelain  crucible.  The  mass  is  then  dissolved  in  dilute  nitric 
acid  and  the  chlorine  again  determined.  The  increase  in  the  percentage 
of  chlorine,  multiplied  by  3-4556,  gives  the  percentage  of  NaC104. 

Tf,  besides  perchlorate,  the  nitre  contains  also  chlorate,  the  latter  is  cal 
culated  as  perchlorate. 

5.  Nitrogen. — See  General  Methods,  3,  B. 

6.  Determination  of  the   Sodium  Nitrate.-  The   amount   of  NaNO3 
may  be  calculated  by  multiplying  the  percentage  of  nitrogen  by  6-0714. 
Usually,  however,  and  especially  with  nitre  for  industrial  purposes,  the 
nitrate  is  determined  either  by  decomposing  it  with  sulphuric  acid  in  presence 
of  mercury  and  measuring  the  volume  of  nitric  oxide  formed,  or  by  difference 
after  the  extraneous  substances  have  been  estimated.     The  methods  to 
be  applied  in  the  twro  cases  are  as  follows  : 

i.  NITROMETRIC  METHOD  (Lunge).  This  makes  use  of  the  Nitrometer, 
shown  in  Fig.  4,  and  consisting  of  two  glass  tubes,  A  and  B,  the  former 


SODIUM  NITRATE   (CHILI   SALTPETRE) 


127 


FIG.  4 


graduated,  connected,  by  rubber  tubing.  Mercury 
is  poured  into  B  and  forced  into  A  by  j  opening 
the  tap  r  and  raising  B  ;  in  this  way  A  is  rilled  with 
mercury  (care  being  taken  that  no  air  bubbles 
remain  along  the  walls  of  the  tube)  to  the  tap, 
which  is  then  closed. 

From  0-35  to  0-45  gram  of  the  finely  powdered 
nitrate  (which  gives  not  less  than  100  and  not 
more  that  130  c.c.  of  NO)  are  placed  in  the  funnel 
i  in  which  it  is  shaken  with  about  0-5  c.c.  of  hot 
water  until  dissolved.  Tube  B  is  then  lowered 
and  the  tap  r  carefully  opened,  so  that  the  solu- 
tion, but  no  air,  enters  A.  The  funnel  is  washed 
with  not  more  than  i  c.c.  of  hot  water,  which  is 
also  cautiously  introduced  into  A .  Finally  about 
15  c.c.  of  pure  cone,  sulphuric  acid  are  run  into  A, 
which  is  shaken  vigorously  to  induce  the  reaction 
between  nitrate,  sulphuric  acid  and  mercury,  by 
which  the  whole  of  the  nitrogen  of  the  nitrate  is 
converted  into  nitric  oxide.  After  the  lapse  of  at 
least  half  an  hour,  the  tube  B  is  raised  until  the 
mercury  is  at  the  same  level  in  A  and  B,  the 
volume  of  the  gas  being'  read,  and  also  the  tem- 
perature and  barometric  pressure. 

The  volume  of  the  gas  (V)  at  o°  and  760  mm.  is  given  by  the  formula, 

vp 

r,  where  v  is  the  volume  of  the  gas  in  the  nitrometer, 
760(1  +  o -00367^ 

p  the  atmospheric  pressure  and  t  the  temperature.     The  amount  of  NaNO3 
in  the  quantity  of  nitrate  taken  is  equal  to  0-0038  times   V. 

2.  INDIRECT  METHOD.  The  moisture,  insoluble  matter,  chlorine  and 
sulphuric  acid  are  determined  by  the  ordinary  methods,  the  last  two  con- 
stituents being  calculated  as  NaCl  and  Na2SO4.  The  sum  of  the  percentage 
of  these  four  ingredients  is  then  subtracted  from  100,  the  remainder  being 
the  percentage  of  NaNO3. 

V 

Pure  sodium  nitrate  contains  16-5%  of  nitrogen,  while  the  commercial 
products  for  fertilising  purposes  generally  contain  about  15%.  The  mean  com- 
position of  the  Chili  saltpetre  coming  to  Europe  is  : 

Sodium  nitrate          .......     94-96% 

Sodium  chloride         .......     about  i% 

Sodium  sulphate        .......,,       0-5% 

Insoluble  matter        .          .          .          .          .          .  ,,       0-2% 

Moisture  ...........       2% 

Among  the  impurities  of  importance  in  sodium  nitrate  is  perchlorate  (harm- 
ful), which  may  be  present  in  proportions  varying  from  0-3  to  5-6%,  but  is 
usually  about  i%  ;  the  percentage  of  chlorate  varies  from  o-i  to  i.  Commer- 
cial sodium  nitrate  may  be  adulterated  with  salts  almost  devoid  of  fertilising 
value,  such  as  sodium  sulphate,  and  samples  containing  20-40%  and  even  60% 
of  this  salt  have  been  met  with. 


128  PHOSPHATES 

Other  Nitrates 

Potassium  and  Calcium  nitrates  are  also  used  in  agriculture.  In  the 
former  the  nitrogen  is  estimated  as  in  sodium  nitrate  and  the  other  tests 
indicated  in  the  article  on  potassium  nitrate  (chapter  on  "  Chemical  Pro- 
ducts "),  and  the  determination  of  the  potassium  may  also  be  carried  out 
(see  General  Methods,  5).  With  calcium  nitrate  the  determination  of  the 
nitrogen  is  usually  sufficient. 

The  calcium  nitrate  (obtained  from  synthetic  nitric  acid)  now  sold  as  a  fer- 
tiliser is  of  various  kinds  :  neutral,  with  about  13%  N  ;  basic,  with  10%  N  ;  and 
nitrato-nitrite,  with  14-5%  N. 

CALCIUM    CYANAMIDE 

The  commercial  product  is  a  greyish-black,  fine  or  granulated  powder 
and  consists  of  a  mixture  of  calcium  cyanamide  (CaCN2)  with  lime,  carbon 
and  various  impurities  (calcium  carbide,  sulphur  and  phosphorus  compounds, 
silica,  etc.). 

Its  value  depends  essentially  on  its  nitrogen  content,  which  is  deter- 
mined by  Ulsch's  modified  Kjeldahl  method  (see  General  Methods,  3,  C) 
on  0-5-1  gram  of  substance.  The  action  is  to  be  regarded  as  complete  after 
about  three  hours'  boiling  with  phosphosulphuric  acid,  since  the  liquid 
does  not  become  clear  and  colourless  owing  to  the  presence  of  carbon  in 
suspension.  It  is  also  sufficient  to  boil  i  gram  of  the  substance  for  2  hours 
with  30  c.c.  of  dilute  sulphuric  acid  (i  :  i)  and  a  drop  of  mercury. 


* 
*  * 


Pure  calcium  cyanamide  (CaCN2)  contains  33%  N  ;  the  commercial  product, 
consisting  on  the  average  of  60%  of  the  cyanamide,  20%  of  lime,  10%  of  car- 
bon and  10%  of  various  extraneous  substances,  contains  15-22%  N. 


Phosphatic  Fertilisers 

PHOSPHATES 

By  phosphates  are  understood  products  containing  tricalcium  phos- 
phate, Ca3(PO4)2,  such  as  Mineral  phosphates  (phosphorites,  apatites,  copro- 
lites)  ;  bones,  such  as  bone  meal  and  bone  ash  ;  and  bone  black. 

Analysis  of  these  products  includes  mainly  determinations  of  the  mois- 
ture and  phosphoric  anhydride  ;  in  some  cases  also  the  nitrogen  (in  bones 
and  the  ash  of  raw  bones),  ferric  oxide  and  alumina  (in  mineral  phosphates) 
and  others  indicated  in  5  (below),  when  a  complete  analysis  is  required. 

1.  Moisture. — See  General  Methods,  2. 

2.  Phosphoric  Anhydride  (total). — See  General  Methods,  4. 

3.  Nitrogen. — See  General  Methods,  3,  C. 

4.  Ferric    Oxide   and    Alumina. — Glaser's   method.     5  grams  of  the 
substance  are  boiled  for  about  30  minutes  in  a  250  c.c.  measuring  flask 
with  50-75  c.c.  of  water,  20  c.c.  of  cone,  hydrochloric  acid  and  5  c.c.  of  cone, 
nitric  acid,  the  liquid  being  made  up  to  volume  on  cooling  and  filtered. 


PHOSPHATES  129 

50  c.c.  of  the  filtrate  (=  i  gram  of  substance)  are  shaken  in  another  250  c.c. 
flask  with  50  c.c.  of  water  and  25  c.c.  of  cone,  sulphuric  acid,  allowed  to 
stand  for  about  15  minutes  and  then  well  shaken  with  100  c.c.  of  95-96% 
alcohol.  When  quite  cold,  the  liquid  is  made  up  to  volume  with  alcohol, 
mixed  and  again  made  up  to  volume  (contraction  occurring)  ;  after  mix- 
ing, the  solution  is  left  for  at  least  30  minutes  and  filtered.  100  c.c.  of  the 
filtrate  (=  0-4  gram  of  substance)  are  evaporated  almost  to  dryness  in  a 
porcelain  dish  and  the  residue  taken  up  in  water,1  heated  on  a  water-bath 
and  treated  with  a  slight  excess  of  ammonia,  which  precipitates  the  iron 
and  aluminium  as  phosphates.  The  heating  is  continued  until  the  excess 
of  ammonia  is  expelled,  the  liquid  being  filtered  when  cold  and  the  precipi- 
tate washed  with  hot  water,  dried,  ignited  and  weighed.  The  weight, 
divided  by  2,  gives  Fe2O3  +  A12O3  in  0-4  gram  of  substance. 

5.  Other  Determinations. — For  complete  analysis,  which  is  required 
more  especially  with  mineral  phosphates,  the  determinations  indicated 
briefly  below  z  are  necessary  in  addition  to  those  given  above  : 

Fluorine,  by  transformation  into  silicon  fluoride  by  treatment  with 
silicious  sand  and  sulphuric  acid,  the  fluoride  being  subsequently  decom- 
posed by  water  and  the  hydro fluosilicic  acid  formed  titrated  (Penfield's 
or  Offermann's  method). 

Chlorine,  by  dissolving  the  phosphate  in  nitric  acid  and  estimating  the 
chlorine  volumetrically  by  the  usual  methods. 

Sulphuric  acid,  by  precipitation  as  barium  sulphate  from  the  hydro- 
chloric acid  solution  of  the  phosphate. 

Carbon  dioxide,  by  treatment  of  the  phosphate  with  an  acid  and  absorp- 
tion of  the  carbon  dioxide  by  potassium  hydroxide  in  the  usual  manner. 

Silica,  by  treatment  of  the  substance  with  aqua  regia  so  as  to  render  the 
silica  insoluble. 

Manganese,  by  dissolving  the  substance  in  aqua  regia,  eliminating  the 
iron,  phosphates,  etc.,  by  means  of  zinc  oxide  and  titration  of  the  mangan- 
ous  salt,  remaining  in  solution,  with  permanganate. 

Lime,  by  weighing  the  calcium  sulphate  remaining  undissolved  in  alcohol 
in  the  determination  of  the  oxides  of  iron  and  alumina  by  Glaser's  method 
(see  4),  or  by  dissolving  the  substance  in  hydrochloric  acid,  precipitating 
with  ammonia,  redissolving  in  acetic  acid  and  separating  the  lime  as  oxalate. 

Magnesia,  by  precipitation  as  magnesium  ammonium  phosphate  after 

elimination  of  the  lime. 

* 
*  * 

Mineral  phosphates  may  contain  (%)  :  moisture,  0-3-8  ;  P2O6,  10-55  ;  CaO, 
22-57  '•  A12O3  +  Fe2O3,  0-2-10  ;  CO2,  2-24  ;  SiO2,  2-8.  Small  amounts  of 
fluorine  (more  than  0-1%  CaF2)  and  manganese  are  almost  always  present. 

Bones  and  bone  ash  may  contain  37-40%  P2O5,  and  up  to  about  4%  N. 

Bone  black   (refinery  waste,   etc.)   usually  contains    20-40%   of  water  and 

25-30%  P2o5. 

1  If  the  phosphate  contains  organic  substances,  it  is  well  at  this  point  to  take  up 
with  hydrochloric  acid  and  a  few  drops  of  bromine,  to  boil  until  bromine  vapours  dis- 
appear, to  dilute  with  water,  and  to  precipitate  with  ammonia  as  above. 

2  The  detailed  methods  may  be  found  in  special  works  dealing  with  the  analysis  of 
fertilisers  or,  more  particularly,  of  phosphates. 

A.C.  9 


130  SUPERPHOSPHATES 

SUPERPHOSPHATES 

In  these  products  the  phosphoric  acid  occurs  mostly  as  monocalcium 
phosphate,  Ca(H2PO4)2,  and  to  a  less  extent  as  dicalcium  phosphate, 
CaHPO4,  that  is,  in  two  forms  soluble  in  water  and  in  ammonium  citrate  ; 
smaller  quantities  may  occur  as  tricalcium  phosphate,  insoluble  in  water 
or  the  citrate,  but  soluble  in  acids.  Superphosphates  contain  also  free 
phosphoric  and  sulphuric  acids,  calcium  sulphate,  silica  and  other  extraneous 
substances,  according  to  their  origin  (see  later). 

Superphosphates  are  distinguished  as  bone  superphosphates  ;  mineral 
superphosphates  ;  and  double,  triple  and  enriched  superphosphates,  which 
are  obtained  by  treating  the  phosphates  with  phosphoric  acid. 

The  analysis  of  these  products  includes  the  following  : 

1.  Moisture. — See  General  Methods,  2. 

2.  Phosphoric  Anhydride. — That  soluble  in  water  and  ammonium 
citrate,  and  that  soluble  in  water  alone,  are  determined. 

A.  PHOSPHORIC  ANHYDRIDE  SOLUBLE  IN  WATER  AND  IN  AMMONIUM 
CITRATE  (Appiani's  method).  This  requires  the  solutions  (ammonium 
citrate,  magnesia  mixture  and  ammonia)  prescribed  for  the  determination 
of  the  total  phosphoric  acid  (see  General  Methods,  4)  :  5  grams  of  the  super- 
phosphate (2-5  grams  with  double  or  triple  superphosphate)  are  made  into 
a  paste  in  a  mortar  with  40-50  c.c.  of  water,  allowed  to  stand  a  few  minutes 
and  the  liquid  decanted  on  to  a  pleated  filter,  the  filtrate  being  collected  in 
a  250  c.c.  measuring  flask.  This  treatment  with  water  is  repeated  three  or 
four  times,  the  operations  being  regulated  so  that  the  digestion  lasts  only  a 
few  minutes  and  the  filter  is  always  empty  when  the  decanted  liquid  is  placed 
in  it.  The  whole  of  the  solid  matter  is  finally  washed  on  to  the  filter  and 
there  washed  until  the  volume  of  the  total  filtrate  occupies  nearly  250  c.c.  ; 
a  few  drops  of  hydrochloric  or  nitric  acid  are  then  added  and  the  volume 
made  up  with  water  (aqueous  solution). 

The  filter  and  its  contents  are  introduced  into  another  250  c.c.  measuring 
flask  and  digested  with  100  c.c.  of  the  ammonium  citrate  solution  1  for  an 
hour  at  35-40°,  with  frequent  shaking  ;  when  cool,  the  volume  is  made 
up  to  250  c.c.  with  water  and  the  liquid  shaken  and  filtered  (citric 
solution). 

To  50  c.c.  of  the  aqueous  solution  are  added  50  c.c.  of  the  citric  solution, 
50  c.c.  of  water,  50  c.c.  of  ammonia  (D  0-92)  and  then,  gradually  and  with 
shaking,  50  c.c.  of  magnesia  mixture.  After  the  whole  has  been  well  shaken, 

1  This  amount  of  citrate  is  usually  more  than  sufficient  to  dissolve  all  the  dicalcium 
phosphate  in  the  residue  insoluble  in  water  from  ordinary  commercial  superphosphates, 
in  which  form  four-fifths  to  nine-tenths  of  the  phosphoric  acid  soluble  in  citrate  is  soluble 
in  water.  With  precipitated  phosphates,  with  superphosphates  of  high  grade  but 
poor  in  phosphoric  acid  soluble  in  water,  and  with  phosphates  quite  free  from  monocal- 
cium phosphate,  so  that  part  of  the  phosphate  might  remain  undissolved,  it  is  advisable 
to  use  more  citrate  or  to  work  with  a  smaller  quantity  of  substance. 

With  double  and  triple  superphosphates,  meat  guano,  or  excessively  dry  super- 
phosphates, in  order  to  include  also  any  pyro-  and  meta-phosphoric  acids  present  it  is 
advisable,  before  precipitating  the  phosphoric  acid,  to  heat  the  solution  for  some  time 
with  a  little  nitric  acid  to  transform  into  phosphoric  acid  the  pyro-  and  meta-phosphoric 
acids  which  may  be  formed  during  drying. 


SUPERPHOSPHATES  131 

the  procedure  is  as  indicated  on  p.  123  for  the  determination  of  the  total 
phosphoric  acid.     Mg2P2O7  X  0-64  =  P20S  per  i  gram  of  substance. 

B.  PHOSPHORIC  ANHYDRIDE  SOLUBLE  IN  WATER.  To  50  c.c.  of  the 
aqueous  solution  prepared  as  in  A  are  added  20  c.c.  of  ammonium  citrate, 
50  c.c.  of  water,  50  c.c.  of  ammonia  (D  0-92)  and  50  c.c.  of  magnesia  mix- 
ture. This  is  shaken  and  treated  exactly  as  in  A. 

3.  Nitrogen.— This  is  determined  particularly  in  bone  superphosphate 
or  for  the  detection  of  adulteration  (see  5)  by  Ulsch's  modification  of  the 
Kjeldahl  method  (see  General  Methods,  3,  C). 

4.  Degree  of  Fineness. — 25  or  50  grams  of  the  superphosphate  simply 
mixed  with  a  spatula  (not  powdered)  are  sieved  for  5  minutes  through  a 
sieve  of  1-2  mm.  mesh,  the  percentage  passing  through  being  determined. 

5.  Adulterations. — These  should  be  tested  for  with  so-called  bone 
superphosphates,  which  have  the  greatest  value  and  are  therefore  the  most 
often  adulterated.     As  adulterants,  use  is  made  more  particularly  of  mineral 
superphosphates,  bone  ash,  bone  black  ;    precipitated  phosphates  ;    pyro- 
phosphates  and  superphosphates  obtained  from  them  ;  gypsum,  calcareous 
substances  (chalk,  powdered  oyster  shells)  ;  sand,  road  dirt  ;  various  organic 
nitrogenous  substances  (dried  blood,  leather  or  wool  waste,  residues  from 
the  purification  of  illuminating  gas). 

The  detection  of  adulteration  in  bone  superphosphate  is  not  always  easy 
or  certain.  Preliminary  tests  to  distinguish  bone  from  mineral  superphos- 
phate and  to  detect  certain  other  adulterants  are  as  follows  : 

(a)  The  sample  is  made  into  a  paste  with  water  and  filtered  :    bone 
superphosphate  gives  a  clear,  coloured  filtrate,  whereas  mineral  superphos- 
phate gives  a  turbid,  colourless  one. 

(b)  The  sample  is  heated  in  a  porcelain  dish  over  an  ordinary  flame  until 
charred  and  then  in  a  platinum  dish  over  a  blowpipe  flame  vigorously  and 
for  a  long  time.     Bone  superphosphates  give  no  white  fumes,  but  only  an 
odour  of  sulphur  dioxide,  and  a  white  or  faintly  yellow,  incandescent  mass, 
which  is  white  or  barely  reddish  when  cold ;  mineral  superphosphates  give  white 
fumes  of  SO3  and  a  mass  which  is  yellow  when  hot  and  brick-red  in  the  cold. 
Further,  the  residue  from  bone  superphosphate  is  completely,  or  almost 
completely,  soluble  in  hot  10%  hydrochloric  acid,  whilst  mineral  superphos- 
phate leaves  a  more  or  less  abundant  residue  insoluble  in  the  dilute  acid. 

(c)  The  aqueous  solution  of  the  sample  is  tested  for  chloride,  a  marked 
proportion  of  the  latter  indicating  the  presence  of  precipitated  phosphate. 

(d)  Abundant  effervescence  when  the  sample  is  treated  with  hydrochloric 
acid  indicates  addition  of  calcareous  substances. 

A  complete  examination  requires,  however,  systematic  investigations 
and  determinations  including  :  microscopic  observations  or  a  petrographical 
study,  determinations  of  the  total  and  citrate-soluble  phosphoric  acid,  sul- 
phuric anhydride,  silica,  insoluble  residue,  nitrogen  in  the  latter,  fluorine, 
chlorine,  lime,  alumina  and  ferric  oxide  and  manganese.1 

1  See  E.  Lasne  :  "  Detection  of  Adulteration  of  Bone  Superphosphate  "  (Staz.  sper. 
agrar.  ital.,  1898,  p.  270)  ;  F.  Martinotti  :  "A  Method  for  Distinguishing  Bone  Phos- 
phates from  Mineral  Phosphates  "  (ibid.,  1897,  p.  663)  ;  G.  Masoni  :  "  Contribution  to  the 
Detection  of  Adulterants  in  Bone  Superphosphate  "  (ibid.,  1910,  p.  297). 


132  SLAGS 

Commercial  superphosphates  contain  14-20%  of  P2O5  soluble  in  water  and 
citrate;  their  strength,  in  percentage  of  P2O5,  is  only  guaranteed  as  14/16, 
15/17,  16/18,  18/20.  The  normal  percentage  of  moisture  is  10-15  m  mineral 
superphosphates  and  13-16  in  those  from  bones. 

Bone  superphosphates  contain  i— 1-5%  of  organic  nitrogen  and  are  to  be 
regarded  as  genuine  when  they  contain  less  than  0-1%  A12O3  +  Fe2O3,  less 
than  0-1%  CaF2,  less  than  0-05%  CaCl2,  less  than  i%  SiO2,  less  than  0-3%  of 
residue  insoluble  in  acids,  (and  this  is  free  from  nitrogen)  and  no  manganese,  and 
when  the  value  of  the  ratio  CaO  :  P2O5  lies  between  1-30  and  1-35,  that  of  SO3 
X  100  :  total  P2O5  is  110-129,  and  that  of  SO3  X  100  :  soluble  P2O5  =  110-132 
(in  the  last  two  ratios  SO3  and  P2O6  are  referred  to  100  parts  of  dry  sub- 
stance) . 

The  mineral  superphosphates,  on  the  other  hand,  contain  no  nitrogen,  but 
relatively  large  proportions  of  alumina  and  ferric  oxide,  fluorine,  silica  and 
insoluble  residue  ;  further  the  ratio  SO3  X  100  :  total  P2O5  =  181-227  and  SO3 
X  ioo  :  soluble  P2O5  =  184-242  (SO3  and  P2O5  referred  to  dry  substance). 

Double  and  triple  superphosphates  contain  40-45%  P2O5. 


SLAGS 

Dephosphorisation  slag,  or  Thomas  slag,  forms  a  fine,  brownish-grey 
powder,  and  it  contains  calcium  phosphate,  mostly  (75-70%  of  the  total 
P2O5)  soluble  in  ammonium  citrate  or  citric  acid,  and  on  this  its  value  depends. 
Analysis  of  this  product  comprises  the  following  : 

1.  Total  Phosphoric  Anhydride   (Loge's  method). — 5  grams  of  sub- 
stance, placed  in  a  250  c.c.  measuring  flask,  are  moistened  with  water,  25- 
30  c.c.  of  cone,  sulphuric  acid  added,  and  the  flask,  covered  with  a  funnel, 
heated  on  a  gauze  or  sand-bath  until  white  vapours  are  emitted  ;  the  liquid 
is  then  diluted  with  water,  allowed  to  cool,  made  up  to  volume  with  water 
and  mixed.     To  50  c.c.  of  the  filtered  liquid  (=  i  gram  of  substance)  are 
added  20  c.c.  of  ammonium  citrate,  50  c.c.  of  water,  50  c.c.  of  ammonia 
(D  =  0-92),  and  50  c.c.  of  magnesia  mixture,  the  procedure  then  being  that 
for  the  ordinary  determination  of  total  phosphoric  anhydride  (see  General 
Methods,  4). 

2.  Phosphoric  Anhydride  soluble  in  Citric  Acid  (Wagner's  method}. 
— The  following  solutions  are  required  : 

(a)  Citric  Acid,     ioo  grams  of  the  crystallised  acid  and  0-05  grain  of 
salicylic  acid  are  dissolved  in  water  to  i  litre.     Immediately  before  use,  i 
vol.  of  this  solution  is  diluted  with  4  vols.  of  water,  this  giving  the  2%  citric 
acid  solution  necessary  for  the  determination. 

(b)  Molybdic  solution.     150  grams  of  pure  ammonium  molybdate  are 
dissolved  in  500  c.c.  of  water  and  the  solution  poured  into  i  litre  of  nitric 
acid  (D  1-19),  400  grams  of  ammonium  nitrate  being  added,  the  volume 
made  up  to  2  litres  with  water,  the  liquid  left  at  about  35°  for  24  hours  and 
then  filtered. 

(c)  Magnesia  mixture.    This  is  prepared  as  indicated  on  p.  123. 
MODE  OF  WORKING  : 

5  grams  of  slag,  in  a  graduated  500  c.c.  flask,  are  moistened  with 
5  c.c.  of  alcohol  and  the  volume  made  up,  gradually  and  with  thorough 
shaking,  with  the  2%  citric  acid  solution.  It  is  then  rotated  mechanically 


SLAGS  133 

at  30-40  turns  per  minute  for  half  an  hour  at  a  temperature  of  17-5°,  and 
immediately  afterwards  filtered. 

In  a  cylindrical  beaker,  50  c.c.  of  the  filtrate  (=  0-5  gram  of  substance) 
are  heated  on  a  water-bath  at  65°  for  15  minutes  with  80-100  c.c.  of  the 
molybdic  solution  (b).  When  cool,  the  mixture  is  filtered  and  the  ammonium 
phosphomolybdate  washed  with  i%  nitric  acid  and  dissolved  in  about  100 
c.c.  of  2%  ammonia  ;  after  addition  of  15  c.c.  of  magnesia  mixture  (c)  and 
shaking,  the  procedure  is  as  in  the  determination  of  the  total  phosphoric 
anhydride  (see  p.  123). 

3.  Free  Lime.  —  10  grams  of  the  slag  are  treated  with  about  250  c.c. 
of  water  in  a  500  c.c.  measuring  flask,  with  frequent  shaking  over  several 
hours.     When  the  volume  has  been  made  up  with  water  and  the  liquid 
mixed  and  filtered,  50  or  100  c.c.  (—  I  or  2  grams  of  substance)  are  titrated 
with  N/2-hydrochloric  acid  and  phenolphthalein.     i  c.c.  N/2-HC1  —  0-014 
gram  CaO 

4.  Degree  of  Fineness.  —  50  grams  of  the  slag  as  received  are  sieved 
for  15  minutes  with  a  No.  100  Kahl  sieve  20  cm.  in  diameter.     The  weight 
remaining  in  the  sieve  is  subtracted  from  50  grams  and  the  remainder  multi- 
plied by  2  to  give  the  percentage  of  fine  slag. 

5.  Specific  Gravity.  —  This  is  determined  with  an  ordinary  picnometer, 
alcohol  or  essence  of  turpentine  being  used  as  the  liquid. 

6  .  Adulterations  .  —  Thomas  slag  is  adulterated  with  mineral  phosphates, 
aluminium  phosphate  or  Redonda  phosphate,  Martin  slag,  Wolter  and 
Wiborg  phosphates  (artificial  slags)  and  coal  dust. 

For  detecting  natural  phosphates  and  aluminium  phosphate,  recourse 
may  be  had  to  microscopic  examination,  to  determinations  of  the  specific 
gravity,  of  the  loss  on  ignition  and.  of  the  portion  soluble  in  hot  water  and 
to  tests  for  fluorine,  carbonates  and  alumina  (the  slag  is  shaken  in  the  cold 
with  sodium  hydroxide  solution  and  the  liquid  filtered,  acidified  with  hydro- 
chloric acid  and  tested  with  ammonia). 

Martin  slag  and  Wolter  and  Wiborg  phosphates  are  indistinguishable 
from  the  Thomas  slag,  but  in  general  are  less  rich  in  phosphoric  anhydride. 

Coal  dust  may  be  observed  under  a  lens  or  by  shaking  the  slag  with 
water  (the  coal  floats). 


Genuine  Thomas  slag  contains  11-23%  °f  total  P2O6  (on  the  average  about 
17%)  and  9-5-16%  of  P2O5  soluble  in  citric  acid  (on  the  average,  12-5-13-5%). 
It  contains  also  41-52%  of  total  CaO  (mean,  46-47%),  3-6%  MgO,  9-28%  of 
ferroso-ferric  oxide  (mean,  about  15),  3-8%  SiO2  (mean,  about  7),  and  about 
10%  of  matter  soluble  in  hot  water.  It  contains  only  very  small  quantities  of 
alumina  and  no  fluorine,  and  on  calcination  loses  not  more  than  i  %  of  its  weight. 
Its  specific  gravity  is  3-3-3,  and  under  the  microscope  it  is  seen  to  be  composed  of 
small,  yellowish,  acute-angled  splinters. 

As  regards  the  testing  of  the  genuineness  of  mineral  phosphates,  it  must  be 
borne  in  mind  that,  unlike  Thomas  slag,  these  do  not  contain  P2O5  soluble  in 
citric  acid,  and  are  almost  entirely  insoluble  in  hot  water  ;  on  ignition,  they  lose 
considerably  in  weight  (water,  CO  2)  ;  they  contain  fluorine  ;  their  specific 
gravities  are  below  3,  and  under  the  microscope  they  are  seen  to  consist  of  round- 
ish granules.  Redonda  phosphate  is  detected  by  testing  for  aluminium  (abundant 
precipitate  in  test  6). 


134  POTASH   FERTILISERS 

PRECIPITATED    PHOSPHATE 

Fine,  yellowish  white  powder,  composed  essentially  of  dicalcium  phos- 
phate, CaHPO4,  and  hence  mostly  soluble  in  ammonium  citrate. 

Consequently,  the  citrate-soluble  phosphoric  anhydride  is  determined 
in  these  products,  using  the  method  employed  with  superphosphates  (see 
Superphosphates,  observing  note  i  on  p.  130). 

Any  adulteration  with  mineral  phosphate,  gypsum  or  chalk,  may  be 
detected  as  in  superphosphates. 

Precipitated  calcium  phosphate  contains  on  an  average  40-42%  P2O5 
soluble  in  citrate,  and  2-3%  P2O5  insoluble  in  citrate  but  soluble  in  acids,  7-8% 
of  moisture,  2-3%  of  chlorine  (chloride  resulting  from  the  method  of  prepara- 
tion) and  small  proportions  of  alumina,  ferric  oxide  and  sulphates. 

Potash  Fertilisers 

The  most  important  potash  fertilisers  consist  of  Stassfurt  salts,  those 
most  used  being  ordinary  potassium  chloride  and  sulphate.  Use  is  also 
made  of  carnallite  (potassium  and  magnesium  chlorides,  with  magnesium 
sulphate  and  sodium  chloride)  ;  kainit  (potassium  and  magnesium  sulphates, 
with  magnesium  and  sodium  chlorides)  ;  sylvine  (sodium  and  potassium 
chlorides,  with  sulphates)  ;  hard  salt  (composition  similar  to  that  of  Kainit)  ; 
potash  manure  salts  (potassium  chloride  with  varying  proportions 
of  magnesium  sulphate  and  chloride,  sodium  chloride  and  calcium  sulphate). 

The  value  of  these  products  depends  naturally  on  their  content  of  K2O, 
and  for  agricultural  purposes  it  is  sufficient  to  determine  this  by  the  method 
given  on  p.  124. 

Where,  for  special  purposes,  a  complete  analysis  or  at  least  a  knowledge 
of  the  content  of  sodium  chloride  is  required,  the  following  procedure  is 
pursued. 1 

A.     Complete  Analysis 

This  includes  the  following  determinations  : 

1 .  Moisture. — 10  grams  are  heated  at  a  dull  red  heat  in  an  open  plati- 
num crucible  for  10  minutes.     If  the  salt  contains  magnesium  chloride,  it 
is  covered  with  a  layer  of  ignited  quicklime. 

2.  Insoluble   Substances. — 100  grams  of  the  salt  are  dissolved  in 
about  400  c.c.  of  boiling  water,  the  solution  filtered  through  a  tared  filter, 
the  residue  being  well  washed  and  the  filtrate  made  up  to  1000  c.c.      The 
filter  is  then  dried  and  weighed. 

3.  Sulphuric  Acid,  Chlorine,  Lime,  Magnesia. — These  are  deter- 
mined in  aliquot  parts  of  the  above  solution  by  the  ordinary  methods. 

4.  Alkalies. — 100  c.c.  of  the  solution  prepared  as  in  2  (=  10  grams  ot 
substance)  are  introduced  into  a  500  c.c.  flask  and  treated  as  in  B  (below). 

1  More  detailed  notices  on  the  analysis  of  potassium  salts  may  be  found  in  Analyse 
des  engrais,  by  D.  Sidersky  (Paris,  1901),  and  in  a  memoir  by  H.  Roemer  on  "  Methodes 
pour  1'analyse  des  sels  depotasse,"  published  in  Bull,  de  I' association  des  chim.de  sucr., 
1911-1912,  Vol.  29,  p.  849. 


POTASH  FERTILISERS  135 

B.     Determination  of  the  Sodium  Chloride 

In  a  500  c.c.  flask  10  grams  of  the  substance  are  boiled  with  about  250  c.c. 
of  water.  If  marked  quantities  of  sulphate  are  present,  10%  barium  chloride 
solution  is  now  added,  slowly  and  with  shaking,  until  no  further  precipita- 
tion occurs  (excess  is  to  be  avoided)  ;  slight  excess  of  baryta  solution  is  then 
added  to  the  liquid  and  the  latter  boiled  for  about  15  minutes.  With  pro- 
ducts free  from  or  poor  in  sulphate,  the  baryta  solution  alone  is  added. 
When  cool,  the  solution  is  made  up  to  the  mark,  mixed  and  filtered. 

100  c.c.  of  the  filtrate  (=  2  grams  of  substance)  are  heated  to  boiling 
in  a  200  c.c.  flask,  ammonium  carbonate  solution  being  added  gradually 
and  with  shaking  to  the  boiling  liquid  as  long  as  any  precipitate  forms. 
The  solution  is  then  heated  (not  boiled)  until  the  precipitate  becomes  crystal- 
line, and  when  cold  made  up  to  volume  with  recently  boiled  water,  mixed 
and  filtered. 

Of  the  filtrate,  100  c.c.  (=  i  gram  of  substance)  are  evaporated  to  dry- 
ness  in  a  platinum  dish  and  the  residue  gently  heated  to  eliminate  the  ammo- 
nium salts,  dissolved  in  a  little  hot  water  and  filtered  through  a  small  filter. 
The  dish  and  filter  are  washed  with  hot  water  and  the  whole  of  the  liquid 
evaporated  to  dryness  in  a  tared  platinum  dish,  which  is  then  dried  in  an 
oven,  heated  gently  at  a  dull  red,  and  weighed. 

The  sodium  and  potassium  chlorides  corresponding  with  I  gram  of  sub- 
stance are  obtained  in  this  way.  The  amount  of  sodium  chloride  in  the 
mixed  chlorides  may  be  determined  by  two  methods  : 

1.  The  potassium  is  determined  as  platinichloride  or  perchlorate   (see 
p.  125).     K2PtCl6  X  0-307  =  KC1 ;    KC1O4  X  0-538  =  KC1.      This  method 
is  preferable  when  one  of  the  two  chlorides  greatly  predominates. 

2.  The  chlorine  in  the  mixed  chlorides  is  determined  volumetrically  (by 
dissolving  to  a  definite  volume  and  titrating  an  aliquot  part  of  the  solution 
with  N/io-AgNOg  according  to  Volhard's  method),  the  quantity  of  NaCl 
(x)  being  calculated  from  the  formula, 

x  =  (px  7-64632)  —  (P  x  3-63354)> 

in  which  p  =  grams  of  Cl  in  the  mixed  chlorides  and  P  the  weight  of  the  pure 
chlorides  obtained  from  i  gram  of  the  substance. 

* 
*   * 

The  strength  (%  K2O)  of  potassium  salts  is  usually  guaranteed  as  follows  : 

Kainit,  minimum  12-4,  but  also  13,  13-5,  14,  14-5  and  15. 

Carnallite,  9  ;    high  quality  carnallite,   13. 

Sylvine,  minimum  12-4,  but  also  sold  up  to  16-20. 

Hard  salt,  minimum  12-4. 

Potassium  chloride,  minimum  56-8  for  90-95%  KC1  ;    50-5  for  80-85%  KC1. 

Potassium  sulphate,  51-8  (96%  K2SO4)  and  48-6  (90%  K2SO4). 

Potassium  and  magnesium  sulphate,  25-9. 

Potash  manure  salts,   15,  20,   30,  38,   40,  42. 

A  certain  importance  as  a  fertiliser  with  a  potash  basis  attaches  to  the 
potash  salt  obtained  by  incinerating  residues  from  the  fermentation  and  distil- 
lation of  molasses.  It  consists  mostly  of  potassium  carbonate  and  its  strength 
(%  of  K20)  is  45-49-5- 


136 


Complex  Fertilisers 


These  include  nitrogen-phosphate-potassium  fertilising  materials  such  as 
stable  manure  and  other  excrements,  guano,  dried  blood,  meat  waste,  silkworm 
chrysalides,  residties  of  wool,  hair,  feathers,  leather,  horn,  nails,  etc.,  oleaginous 
seed  cake,  peat,  various  industrial  residues  and  artificial  mixtures  of  mineral 
or  organic  and  mineral  fertilisers. 

Analysis  of  these  products  comprises  essentially  determinations  of  the 
moisture,  nitrogen,  total  phosphoric  acid  and  potash,  these  being  carried 
out  by  the  general  methods  already  described  with  only  such  modifications 
as  are  indicated  below. 


STABLE    MANURE 

The  sample  should  be  taken  from  many  points  of  the  mass  and  should 
be  mixed  without  pressing  it  so  as  to  lose  none  of  the  liquid  portion. 

Analysis  is  made  partly  on  the  product  previously  dried  at  80°  and  partly 
on  the  fresh  product. 

1 .  Water. — 250-500  grams  are  dried  at  70-80°  for  some  hours  and  then 
left  to  cool  in  the  air  and  weighed.     The  dried  mass  is  then  cut  into  small 
portions,  chopped  and  reduced  to  a  fine  powder,  which  is  thoroughly  mixed 
again.     10  grams  of  this  are  then  heated  at  105°  until  of  constant  weight, 
the  total  moisture  being  calculated. 

In  order  to  avoid  any  loss  of  ammonia,  the  total  water  may  be  deter- 
mined as  indicated  in  General  Methods,  2. 

2.  Ash. — 20  grams  of  substance  dried  at  80°  and  powdered,  as  in  i,  are 
incinerated  at  a  dull  red  heat. 

3.  Phosphoric  Acid  and  Potash. — These  are  determined  in  the  ash ; 
see  General  Methods,  4  and  5. 

4.  Nitrogen. — The  ammoniacal  nitrogen  is  determined  on  the  fresh 
manure,  100  grams  of  which  are  distilled  with  magnesium  oxide  ;  the  nitric 
nitrogen  by  protracted  digestion  of  500  grams  with  water,  the  liquid  being 
subsequently  made  up  to  volume  and  the  nitrogen  in  an  aliquot  part  of  the 
filtrate,  corresponding  with  at  least  100  grams  of  substance,  determined  by 
the  Schulze  and  Tiemann  method  ;    the  total  nitrogen,  by  the  Ulsch  (or 
Jodlbaur,  if  nitrates  are  present)  modification  of  Kjeldahl's  method,  on 
100  grams  of  substance  previously  treated  with  200  c.c.  of  phospho sulphuric 
acid  in  the  manner  described  in   the  following  article  :    Other   complex 
fertilisers,  2. 

In  each  case  the  procedure  is  as  prescribed  under  General  Methods,  3,  A, 
B,  and  D. 

The  composition  of  stable  manure  varies,  in  the  majority  of  cases,  between 
the  following  limits  (%)  :  water,  60-80  ;  ash,  5-15  (more  frequently,  10-14)  ; 
total  nitrogen,  0-3-0-8,  small  proportions  only  being  in  the  ammoniacal  condition 
and  very  little  or  none  in  the  nitric  state,  if  the  manure  is  well  preserved  ;  phos- 
phoric anhydride,  0-2-0-5  ;  and  potash,  0-4-1  (usually  0-5-0-6). 


OTHER  COMPLEX  FERTILISERS  137 

OTHER    COMPLEX    FERTILISERS 

The  value  of  the  other  complex  fertilisers  enumerated  on  p.  136,  depends 
essentially  on  their  nitrogen  content,  the  proportions  of  phosphoric  anhy- 
dride and  potash  being  rarely  required. 

Their  analysis  includes  the  following  : 

1.  Moisture. — See  General  Methods,  2. 

2.  Nitrogen. — The  total  nitrogen  (organic)  is  estimated  by  the  Ulsch- 
Kjeldahl  method  (see  General  Methods,  3,  C).     With  voluminous  and  non- 
homogeneous  substances  (hair,  horn,  nails,  and  the  like),  it  is  well  to  heat 
50  or  100  grams  in  a  dish  on  a  water  bath  with  100  or  200  c.c.  cone,  sulphuric 
acid  or  phosphosulphuric  acid,  the  mixture  being  occasionally  shaken,  until 
a  homogeneous  paste  is  obtained.     This  is  made  up  to  a  definite  volume 
with  cone,  sulphuric  acid  and  an  aliquot  part  corresponding  with  1-5  grams 
of  the  original  substance,  according  to  the  presumed  richness  in  nitrogen, 
treated  in  the  ordinary  way. 

3.  Phosphoric   Acid,    Potash.— 10-20  grams  of  the   substance  are 
charred  as  indicated  in  note  i  on  p.  124,  the  phosphoric  acid  and  the  potash 
being  then  estimated  in  the  well  carbonised  product  as  described  in  General 
Methods,  4  and  5. 


* 
*   * 


Guanos  may  contain,  according  to  their  origin  :  nitrogen,  1-19 ;  P2O5; 
1-40;  and  K2O,  0-5-9%.  Peruvian  guano  contains,  on  the  average:  N,  7, 
P2O5,  14  ;  and  K2O,  2%.  Italian  bat  guano  (Sardinia)  contains  about  4%  N,  5% 
P205,  and  i%  K2O. 

In  oil  seed  cake  (arachis,  cameline,  colza,  cotton  seed,  linseed,  sesame,  etc.) 
may  be  found  :  2-7%  N,  0-5-3%  P2O5.  and  0-2-2%  K2O. 

In  peat :  0-3-3%  N,  0-1-0-8%  P2O6,  and  0-1-2%  K2O. 

Various  other  organic  residues  contain  about  7-15%  N,  0-5-2%  P2O6,  and 
°'3-I<5%  K2O.  Exhausted  meat  residues  from  meat- extract  factories  contain 
4-11%  N,  10-25%  P2O6,  and  about  0-5%  K2O. 


CHAPTER  IV 
CEMENT  MATERIALS 

The  principal  elements  of  the  more  important  cement  materials  are 
lime,  silica,  and  alumina. 

The  raw  materials  which  supply  these  elements  are,  more  especially  : 
Limestones,  which  contain  the  lime  ;  marls,  which  contain  lime  and  at 
the  same  time  silica  and  alumina  ;  clays,  pozzolane  and  other  similar 
materials,  and  blast-furnace  slags,  which  contain  the  silica  and  alumina. 

The  cement  materials  composed  essentially  of  lime  are  the  fat  and  lean 
or  poor  limes.  Materials  containing,  besides  lime,  marked  proportions  of 
silica  and  alumina  (clay),  that  is,  the  hydraulic  limes  and  the  cements,  have 
hydraulic  properties,  setting  even  under  water  when  properly  mixed.  Of 
these  the  hydraulic  limes  are  poorer  in  clay  than  the  cements  and  set  more 
slowly. 

Gypsum,  obtained  by  burning  the  hydrated  calcium  sulphate  which 
occurs  abundantly  in  nature,  also  occupies  a  place  among  the  cement 
materials. 

LIMESTONES    AND    MARLS 

Limestones  are  rocks  composed  mainly  of  calcium  carbonate.  Their 
most  common  impurities  are  silica  and  alumina- — the  constituents  of  clay 
— and  ferric  oxide  and  alumina  ;  they  may  also  contain  small  quantities 
of  alkalies,  sulphates,  sulphides,  carbonaceous  and  bituminous  substances 
and  other  impurities.  Limestones  containing  marked  quantities  of  clay 
are  termed  argillaceous  ;  the  name  marl  is  used  in  cases  where  the  clay  is 
in  such  proportion  that  it  cannot  be  regarded  as  an  impurity,  the  material 
being  a  natural  and  intimate  mixture  of  limestone  and  clay. 

Analysis  of  these  materials  aims  principally  at  establishing  the  amounts 
of  calcium  carbonate  and  argillaceous  material  present,  and  in  the  second 
place  at  determining  the  quantities  of  the  various  accessory  components. 

Such  analysis  may  be  partial  or  complete.  The  former  is  far  more 
rapid  and  is  preferred  in  practice,  when  determinations  are  required  only 
of  the  principal  constituents  and  great  accuracy  is  unnecessary. 

138 


LIMESTONES  AND   MARLS  139 

1.    Partial  Analysis 

This  is  limited  to  estimation  of  the  calcium  carbonate  and  any  clay 
present. 

The  proportion  of  calcium  carbonate  may  be  deduced  with  sufficient 
exactness  (when  only  little  magnesia  is  present)  by  a  gasometric  determina- 
tion of  the  carbon  dioxide  (see  later,  Complete  Analysis,  4)  or  by  the  following 
volumetric  method  : 

i  gram  of  the  powdered  material  is  boiled  in  a  flask  with  a  little  water 
and  25  c.c.  of  N-hydrochloric  acid  to  expel  the  carbon  dioxide,  the  excess 
of  acid  in  the  cold  liquid  being  titrated  with  N-caustic  soda  in  presence 
of  cochineal.  The  number  of  c.c.  of  acid  neutralised,  multiplied  by  5,  gives 
the  percentage  of  calcium  carbonate. 

If  this  determination  indicates  that  the  proportion  of  clay  present  is 
not  negligible,  approximate  estimation  is  made  of  the  clay  (regarding  as 
such  the  silica,  plus  the  alumina  and  ferric  oxide).  For  this  purpose  2 
grams  of  substance  are  treated  in  a  fairly  large  porcelain  dish  with  about 
150  c.c.  of 'water  and  10  c.c.  of  concentrated  hydrochloric  acid  (added  care- 
fully), the  liquid  being  boiled  for  some  minutes  and  the  alumina  and  ferric 
oxide  precipitated,  without  preliminary  nitration,  by  slight  excess  of  ammo- 
nia. The  insoluble  matter  (silica)  and  the  precipitate  are  then  collected 
on  a  filter,  washed  5  or  6  times  with  water,  dried,  ignited  at  a  dull  red  heat 
in  a  crucible  and  weighed. 

2.    Complete  Analysis 

For  a  detailed  analysis  of  a  limestone  or  marl  the  following  determina- 
tions are  to  be  made  : 

1.  Moisture  (hygroscopic  water). — 5-10  grams  of  the  finely  powdered 
substance  are  dried  in  an  oven  at  105-110°  until  constant  in  weight. 

2.  Loss    on    Ignition    (combined   water  +  carbon    dioxide  +  organic 
matter). — 1-2  grams  of  the  dry  substance  are  heated  in  a  platinum  crucible, 
at  first  gently  over  a  bunsen  flame  and  later  for  half  an  hour  over  a  blow- 
pipe flame,  this  ignition  being  repeated  until  no  further  loss  of  weight  occurs. 

3.  Combined  Water. — 1-2  grams  of  the  dry  substance  are  heated  in 
a  boat  in  a  hard  glass  tube  traversed  by  a  current  of  dry  air,  the  issuing 
gas  being  passed  through  a  calcium  chloride  tube.     The  increase  in  weight 
of  the  latter  gives  the  combined  water,  while  the  loss  in  weight  of  the  boat 
represents  the  loss  on  ignition.     This  determination  renders  that  given 
under  2   (above)  unnecessary. 

When  organic  matter  is  present,  the  result  of  this  determination  is  not  very 
exact,  the  combined  water  being  increased  by  that  formed  by  the  combustion 
of  the  hydrogen  of  the  organic  matter. 

4.  Carbonic  Anhydride.— This  may  be  estimated  gravimetrically  or 
by  measuring  the  gas  evolved  when  the  substance  is  treated  with  hydro- 
chloric acid. 

(a)  GRAVIMETRIC  METHODS.     These  are  based  on  the  loss  in  weight  of 


140 


LIMESTONES  AND   MARLS 


the  substance  after  treatment  with  hydrochloric  acid,  or  on  the  increase 
in  weight  of  an  apparatus  for  absorbing  the  carbon  dioxide  generated. 

Various  forms  of  apparatus  have  been  designed  to  determine  the  loss 
of  weight,  one  of  the  most  simple  being  that  shown  in  Fig.  5.  It  consists 
of  a  flask  with  a  doubly-bored  stopper,  through  which  pass  (i)  a  bulb  tube 
a  furnished  with  a  cock  and  drawn  out  at  the  bottom,  and  (2)  a  delivery 
tube  terminating  in  a  wider  tube  b  containing  granulated  calcium  chloride 
and  a  little  fused  borax.  Into  the  weighed  flask  a  definite  weight  (about 
i  gram)  of  the  substance  is  introduced,  together  with  a  few  c.c.  of  water, 
the  bulb  being  filled  with  dilute  hydrochloric  acid  and  the  upper  ends  of 
tubes  a  and  b  closed  by  rubber  tubing  and  glass  rod 
plug  or  clip.  The  whole  is  fitted  together  so  that  all 
the  joints  are  air-tight  and  weighed.  The  upper  ends 
of  a  and  b  are  then  opened  and  the  hydrochloric  acid 
allowed  to  flow  gradually  into  the  flask,  a  slow  cur- 
rent of  air  being  drawn  through  the  apparatus  from 
a  to  b.  The  tube  a  is  next  closed  and  the  flask 
heated  gently  on  a  water-bath  and  afterwards  allowed 
to  cool.  Dry  air  is  again  passed  through  the  appar- 
atus for  a  few  minutes,  the  tubes  then  closed  and  the 
whole  weighed,  the  loss  in  weight  giving  the  carbon 
dioxide  in  the  substance  taken. 

More  accurate  is  the  determination  of  the  carbon 
dioxide  by  the  increase  in  weight  of  an  absorption 
apparatus.  This  is  effected  by  introducing  an  exact 
amount  of  the  substance  (about  i  gram)  into  a  flask, 
adding  a  little  water  and  closing  the  flask  with  a 
two-holed  stopper,  through  which  pass  a  reflux  con- 
denser and  a  safety  tube  reaching  almost  to  the 
bottom  of  the  flask  and  terminating  at  the  upper 
end  in  a  tap  which  can  be  connected  either  with  a 
funnel  or  with  a  potash  apparatus  for  purifying  the 
air  from  carbon  dioxide.  The  reflux  condenser  com- 
municates with  a  U-tube  charged  with  glass  beads 
and  concentrated  sulphuric  acid,  beyond  which  come 
first  an  absorption  apparatus  consisting  of  two 
weighed  (J-tubes  containing  soda  lime  and  then  an 

aspirator.  Dilute  hydrochloric  acid  is  poured  on  to  the  substance  by 
means  of  the  funnel,  the  tap  being  then  closed  and  the  funnel  removed. 
Connection  is  next  made  with  the  potash  apparatus,  the  tap  being  opened, 
the  aspirator  started  gently  and  the  flask  gradually  heated  to  boiling. 
Air  is  passed  for  at  least  15  minutes  after  heating  is  discontinued,  the 
absorption  tubes  being  then  disconnected  and  weighed,  the  carbon  dioxide 
in  the  substance  being  thus  determined. 

If  it  is  likely  that  the  substance  contains  sulphides,  it  is  well,  before 
the  reaction,  to  add  a  little  mercuric  chloride  solution  to  retain  the  hydrogen 
sulphide. 

(b)  GASOMETRIC  METHOD.     One  of  the  best  known  forms  of  apparatus 


FIG.  5 


LIMESTONES  AND  MARLS 


141 


for  this  method  is  that  of  Scheibler  and  Dietrich,  of  which  the  essential 
features  are  shown  in  Fig.  6.  It  consists  of  a  wide-necked  bottle  with  a 
perforated  stopper  by  which  it  is  connected  with  a  vertical  tube  c.  The  latter 
is  joined  at  the  top  through  a  3-way  cock— which  can  establish  communi- 
cation also  with  the  outside  air— with  a  graduated  cylinder  a,  which  is 
connected  by  a  rubber  tube  at  the  bottom  with  a  wide  tube  b  capable 
of  being  raised  or  lowered  at  will.  All  joints  must,  of  course,  be  quite 
air-tight. 

From  0-5  to  0*6  gram  of  the  substance  is  placed  in  the  bottle,  together 
with  a  small  tube  containing  hydrochloric  acid,  arranged  so  that,  when 
the  bottle  is  inclined,  the  acid  falls  on  the  sub- 
stance. The  tube  a  is  filled  with  water  (coloured 
red  with  litmus  and  a  little  boric  acid,  to  admit 
of  more  easy  reading)  to  the  top  of  the  gradua- 
tions and  the  pressures  inside  and  outside  of  it 
being  equalised,  the  carbon  dioxide  is  liberated  by 
bringing  the  acid  into  contact  with  the  substance 
in  the  bottle.  The  pressures  are  then  equalised 
and  the  volume  of  the  gas  read  off,  the  result 
being  corrected  in  the  usual  way. 

A  more  convenient  procedure  consists  in 
weighing  such  a  quantity  of  substance — depend- 
ing on  the  temperature  and  pressure  and  deter- 
mined by  means  of  special  tables  1 — -that  the 
volume  of  gas  read  off  gives  directly  the  percent- 
age of  calcium  carbonate  in  the  substance. 

Of  the  other  forms  of  apparatus,  that  of 
Lunge  and  Rittener  may  be  mentioned  as  allow- 
ing of  increased  accuracy. 

5.  Organic  and  Bituminous  Substances. — 
These  are  deduced  by  subtracting,  from  the  loss 
on  ignition,  both  the    combined    water   and   the 
carbon  dioxide,  obtainable  as  under  3  and  4. 

6.  Silica. — (a)    Total    silica.      The   calcined 
substance    (that    remaining    after  the  determina- 
tion of  the  loss  on  ignition)  is  evaporated  to  dry- 
ness  with  a  little  water  and  hydrochloric  acid  in 
a    porcelain    dish,    the    insoluble    residue    being 

stirred  from  time  to  time  with  a  glass  rod.  It  is  then  kept  in  an  oven 
for  about  two  hours  at  110-115°  in  order  to  expel  the  hydrochloric 
acid  completely.2  The  treatment  with  hydrochloric  acid  and  the  evapora- 
tion and  the  drying  in  the  oven  are  repeated  in  order  to  bring  about 
thorough  decomposition  of  the  silicates.  The  dry  residue  is  then  moistened 
with  concentrated  hydrochloric  acid  and  left  to  digest  for  some  hours  in 
the  cold.  It  is  then  taken  up  in  hot  water,  the  solution  filtered  and  the 

1  See    Lunge,    Technical  Methods  of    Chemical  Analysis   (London,    1908),   Vol.  I, 
pp.  66 1   and  662. 

3  Some  consider  that  the  silica  is  rendered  completely  insoluble  only  at  130°. 


FIG.  6 


142  LIMESTONES  AND  MARLS 

residue  washed  by  decantation,  a  few  drops  of  hydrochloric  acid  and  then 
hot  water  being  added  each  time.  The  residue  is  finally  transferred  to  the 
filter,  dried  and  ignited  in  a  platinum  crucible,  the  weight  representing 
silica  and  sand,  together  with  any  silicates  undecomposed.  The  filtrate 
serves  for  the  determination  of  alumina,  iron,  lime  and  magnesia  (see  7 
and  8). 

(b)  Sand  and  combined  silica.  When  the  sand  is  in  marked  quantity 
(this  is  recognized  by  the  fact  that  the  insoluble  residue  is  not  perfectly 
white  and  scratches  when  stirred  in  the  dish  with  a  rod),  it  is  of  interest  to 
determine  it  separately  from  the  combined  silica.  To  this  end  the  insoluble 
residue,  obtained  as  in  the  preceding  case  a  and  not  ignited,  is  heated  in 
the  porcelain  dish  with  200  c.c.  of  10%  sodium  carbonate  (anhydrous) 
solution  for  about  an  hour  on  a  water-bath.  After  filtration,  the  insoluble 
portion  is  washed  by  decantation  with  hot  water,  again  treated  with  sodium 
carbonate  solution  in  the  hot,  collected  on  the  filter,  washed  and  ignited 
in  a  platinum  crucible.  The  weight  of  this  residue  repre- 
sents the  sand  and  any  silicates  remaining  undecomposed. 
In  order  to  make  sure  that  the  latter  are  not  in  ap- 
preciable quantity,  the  residue  is  treated  in  the  platinum 
crucible  with  a  few  drops  of  sulphuric  acid  and  some  c.c. 
of  hydrofluoric  acid,  and  evaporated  on  a  water-bath. 
If  necessary,  further  quantities  of  hydrofluoric  acid  are 
added  until  all  the  silica  is  eliminated  and  the  residue  is 
heated  over  a  small  flame  to  expel  the  sulphuric  acid, 
ignited  and  weighed  ;  the  amount  thus  remaining  should 
be  negligible. 

The  sodium  solution,  containing  the  combined  silica, 
is  acidified  with  hydrochloric  acid,  dried  on  a  water-bath 
and  afterwards  at  110-115°  and  taken  up  in  hydrochloric 
acid,  the  silica  being  filtered  off  and  treated  as  in  a. 

7.  Alumina  and  Ferric  Oxide. — These    are    deter- 
FIG.  7.  mined  together  in  the  filtrate  obtained  from  6,  a  (deter- 

mination of  total  silica).  This  liquid  is  heated  to  boiling 
in  a  porcelain  dish,  any  ferrous  salts  present  being  oxidised  with  a  few 
drops  of  nitric  acid,  and  ammonium  chloride  and  a  slight  excess  of 
ammonia  added.  Heating  is  then  discontinued  and  as  soon  as  the  pre- 
cipitate deposits,  it  is  filtered  off,  washed  at  once  with  boiling  water,  dried 
and  ignited  in  a  platinum  crucible  ;  this  gives  alumina  +  ferric  oxide. 
The  filtrate  is  used  for  subsequent  determinations  (see  8). 

If  the  two  metals  are  to  be  estimated  separately,  the  filtrate  obtained 
in  6,  a  is  made  up  to  a  definite  volume  and  the  two  sesqui-oxides  together 
determined  in  an  aliquot  part  as  above.  In  another  aliquot  part  the  sesqui- 
oxides  are  precipitated  in  the  same  way  and  the  washed  precipitate  dis- 
solved, while  still  moist,  in  hot  dilute  sulphuric  acid,  the  iron  being  then 
reduced  to  the  ferrous  state  by  means  of  zinc  in  a  flask  furnished  with  a 
Bunsen  valve  as  shown  in  Fig.  7.  The  valve  consists  of  a  piece  of  glass 
tube  passing  through  the  stopper  and  joined  to  a  rubber  tube  having  a 
longitudinal  slit  and  closed  at  the  top  with  a  glass  plug.  When  the  reduc- 


LIMESTONES   AND   MARLS  143 

tion  is  complete  and  the  liquid  cold  (one  drop  of  it  should  give  no  coloration 
with  either  potassium  ferrocyanide  or  thiocyanate),  it  is  titrated  with 
standard  permanganate  solution.  The  amount  of  ferric  oxide  alone  is 
thus  obtained. 

8.  Lime   and    Magnesia. — -In  the  filtrate  from  the  aluminium  and 
ferric  hydroxides,  the  lime  is  determined  by  acidifying  faintly  with  hydro- 
chloric acid,  heating  to  boiling  in  a  beaker  and  adding  gradually  a  slight 
excess  of  solid  oxalic  acid  (about  three  times  the  supposed  weight  of  the 
lime  and  magnesia  together).     Ammonia  in  excess  is  then  added,  with 
stirring,  the  precipitate  filtered  off  after  some  hours,  washed  with  cold  water, 
dried,  ignited  in  a  platinum  crucible,  finally  in  a  blowpipe  flame,  and  weighed 
as  CaO. 

In  the  filtrate  from  the  lime  the  magnesia  is  estimated.  To  this  end 
the  liquid  is  acidified  with  hydrochloric  acid,  evaporated  if  necessary  to 
about  200  c.c.  and,  when  cold,  precipitated  in  a  beaker  by  addition  of  40 
c.c.  of  concentrated  ammonia  and  sodium  phosphate  solution.  After  at 
least  12  hours,  the  liquid  is  filtered  and  the  precipitate  washed  with  ammonia 
solution  (1:5)  and  dried,  the  filter-paper  being  burnt  separately  from  the 
precipitate  and  the  whole  ignited  in  a  porcelain  crucible.  If  the  residue  is 
not  white,  it  is  treated  with  a  few  drops  of  nitric  acid  and  again  calcined, 
the  remaining  magnesium  pyro phosphate  being  weighed.  Mg2P2O7  X 
0-36207  =  MgO. 

9.  Sulphates. — In  some  cases  limestone  contains  appreciable  amounts 
of  sulphates  (gypsum),  which  may  be  determined  by  dissolving  a  definite 
weight  (about  2  grams)  in  dilute  hydrochloric  acid,  rendering  the  silica 
insoluble  in  the  usual  way  and  removing  it  by  filtration,  and  precipitating 
with  boiling  barium  chloride  solution.     The  liquid  is  left  for  some  hours 
on  a  water-bath  and -the  precipitate  filtered  off,  washed,  dried  and  ignited  : 
BaSO4  X  0-343  =  SO3. 

10.  Sulphides. — -If  the  limestone  contains  also  sulphur  as  sulphides 
(pyrites,  etc.),  this  may  be  determined  by  dissolving  a  definite  weight  in 
hydrochloric    acid    after    addition    of    a    little    solid    potassium  chlorate. 
The  silica  is  then  separated  as  before  and  the  filtrate  precipitated  with 
barium  chloride.     The  excess  of  the  barium  sulphate  over  that  obtained 
as  in  9  is  derived  from  the  sulphides  :   BaSO4  x  0-13738  =  S. 

11.  Other  Determinations. — -In  rare  cases,  some  other  determina- 
tions may  be  required.     Phosphoric  acid,  for  instance,  is  estimated  by 
precipitation  of  the  nitric  acid  solution  with  ammonium  molybdate,  as 
with  fertilisers.     Determination  of  the  alkalies  is  scarcely  ever  necessary. 

* 
*  * 

The  principal  deductions  drawn  from  the  results  of  analysis  of  a  limestone 
or  marl  are  based  on  the  respective  proportions  of  the  principal  components, 
i.e.,  of  calcium  carbonate  and  clay  (silica  +  alumina  +  ferric  oxide).  Accord- 
ing to  the  content  of  clay,  distinction  is  drawn  between  limestones,  properly 
so  called,  which  contain  only  a  minimal  amount  of  clay  ;  argillaceous  limestones, 
in  which  10%  may  be  present ;  and  marls,  which  are  described  as  calcareous, 
with  ic -2 5%  of  clay,  as  marls  proper  with  25-50%  and  as  argillaceous  marls, 
with  more  than  50%  of  clay.  \Yith  more  than  80%  of  clay,  the  products  may 


144  CLAYS 

be  regarded  as  clays  proper.  These  limits  are  not  absolutely  fast,  passage  from 
one  class  of  substance  to  another  being  gradual.  The  content  of  clay  is  not 
sufficient  to  give  sound  indications  as  to  the  hydraulic  properties  of  the  product 
resulting  from  the  heating,  as  these  depend  also  on  the  method  of  heating  and 
on  the  condition  in  which  the  separate  components  occur. 

As  regards  the  determination  of  the  accessory  components,  this  gives  useful 
indications  when  some  of  them,  such  as  magnesia,  sulphur,  etc.,  are  present  in 
such  quantity  as  to  exert  a  harmful  influence  on  the  quality  of  the  cement 
products  obtained  from  the  materials  analysed. 


CLAYS 

The  essential  constituents  of  clays  are  silica  and  alumina,  while  ferric 
oxide  is  also  habitually  present  ;  as  impurities,  they  may  contain  greater 
or  less  proportions  of  calcium  and  magnesium  carbonates,  alkali  salts, 
sulphates,  pyrites,  and  small  quantities  of  manganese  oxide  and  titanic  acid. 

The  tests  to  be  carried  out  on  clays  vary  according  to  the  uses  to  be 
made  of  the  latter.  Tests  for  clays  to  be  made  into  ceramic  products, 
refractory  materials,  etc.,  will  be  omitted,  only  the  chemical  analysis  of 
clays  for  making  cements  being  considered.  This  analysis  includes  • 

1.  Hygroscopic  Water, — Determined  as  in  limestone. 

2.  Loss  on  Calcination  :    Combined   Water,   Carbon  Dioxide.— 
The  loss  on  calcination  is  determined  as  with  limestone  and  usually  consists 
mainly  of  water.     When  carbonates  or  organic  substances  are  present  in 
sensible  quantities,  the  determination  of  the  combined  water  and  carbon 
dioxide  may  be  made  as  with  limestone. 

3.  Silica. — About  i  gram  of  the*  finely  powdered,  dried  substance  is 
weighed  exactly,  mixed  carefully  with  4-5  times  its  weight  of  dry  sodium  - 
potassium  carbonate  and  heated  in  a  roomy  platinum  crucible  over  a  Bunsen 
flame,  which  is  kept  small  at  first  and  is  gradually  increased  later  so  as  to 
give  a  semi-fused  mass.     The  flame  is  then  maintained  for  at  least  half  an 
hour,  the  mass  being  subsequently  heated  in  the  blowpipe  flame  until  it  is 
completely  fused,  the  disaggregation  thus  requiring  in  all  about  an  hour. 
When  cool,  the  crucible  is  placed  in  a  large  dish  (preferably  of  platinum) 
in  which  it  is  heated  with  water  on  a  water-bath  to  soften  the  mass,  the 
crucible  being  afterwards  removed  with  careful  washing,  and  dilute  hydro- 
chloric acid  gradually  added  until  the  carbonates  are  completely  decom- 
posed.    The  liquid  is  evaporated  to  dryness  on  a  water-bath  and  heated  in 
an  oven  at  110-115°  to  render  the  silica  insoluble,  the  silica  being  then 
treated  as  in  limestone  and  weighed.     The  filtrate  serves  for  the  subsequent 
determinations  indicated  in  4. 

The  weighed  silica  is  then  evaporated  in  the  platinum  crucible  with  a 
few  drops  of  sulphuric  acid  and  about  5  c.c.  of  hydrofluoric  acid,  gently 
ignited  and  weighed  :  the  residue,  usually  only  a  few  milligrams,  consists 
of  alumina,  ferric  oxide  and,  maybe,  titanic  acid,  ?.nd  its  weight  is  sub- 
tracted from  that  of  the  silica  and  added  to  that  of  the  alumina  and  ferric 
oxide  subsequently  found. 

To  estimate  the  sand  separately  from  the  combined  silica,  2-5  grams 
of  the  substance  are  treated  with  cone,  sulphuric  acid  in  a  platinum  crucible, 


CLAYS  145 

most  of  the  acid  being  then  evaporated  on  a  sand-bath  and  the  remainder 
taken  up  in  water  ;  the  clear  liquid  is  decanted  off  and  the  insoluble  residue 
digested  with  hydrochloric  acid  and  then  diluted  with  water  and  heated, 
the  silica  being  filtered  off  and  washed.  Without  being  ignited,  it  is  then 
digested  with  10%  sodium  carbonate  solution,  the  further  procedure  being 
as  with  limestone  (q.v.,  Complete  Analysis,  6,  b). 

4.  Alumina,  Oxides  of  Iron  and  Manganese.  —  In  the  filtrate  from 
the  total  silica  the  iron  is  oxidised  with  nitric  acid  and  precipitated  along 
with  the  alumina,  as  already  described  (see  Limestone,  Complete  Analysis,  7). 

If  manganese  is  present  in  sensible  amount,  the  filtrate  from  the  silica 
is  neutralised  with  sodium  carbonate,  treated  with  neutral  concentrated 
sodium  or  ammonium  acetate  solution,  diluted  with  water  and  heated  to 
boiling  for  a  minute  ;  the  liquid  is  then  filtered  and  the  precipitate  washed 
by  decantation  with  boiling  water  containing  a  little  sodium  or  ammonium 
acetate.  The  precipitate  is  next  redissolved  in  hydrochloric  acid  and  the 
aluminium  and  iron  precipitated  with  ammonia  in  the  ordinary  way.  The 
filtrate  from  the  precipitation  of  the  basic  acetates  is  acidified  slightly  with 
acetic  acid  and  the  manganese  precipitated  as  hydrated  peroxide  by  addition 
of  bromine  water  to  give  a  brown  coloration  and  then  of  excess  of  ammonia, 
the  liquid  being  heated  to  boiling  until  the  precipitate  separates  from  the 
liquid  in  flocks.  After  settling,  the  precipitate  is  filtered,  washed  with 
boiling  water,  dried  and  ignited  in  a  blowpipe  flame  to  transform  it  into 
Mn3O4,  which  is  weighed.  Mn3O4  X  0-93007  =  MnO. 

5.  Lime  and  Magnesia.  —  These  are  determined  in  the  filtrate  from 
the  preceding  determination,  operating  as  with  limestone  (q.v.,  Complete 
Analysis,  8). 

6.  Alkalies.  —  -A  fresh  portion  of  the  substance  (2-5  grams)  is  heated 
in  a  platinum  crucible  on  a  water-bath  with  hydrofluoric  acid  in  presence 
of  a  little  sulphuric  acid,  the  excess  of  acid  being  evaporated  when  all  the 
silica  has  been  expelled.     The  residue  is  then  taken  up  in  hydrochloric  acid 
and  hot  water,  and  the  sulphuric  acid,  aluminium,  iron  and  magnesium 
precipitated  with  excess  of  barium  hydroxide  at  boiling  temperature. 

From  the  filtrate  the  excess  of  baryta  and  the  lime  are  eliminated  by 
digestion  in  the  hot  with  ammonium  carbonate  and  filtration,  the  filtrate 
being  evaporated  to  dryness,  the  residue  heated  to  expel  ammonium  salts, 
the  residue  dissolved  in  water  and  the  solution  filtered  and  evaporated  to 
dryness  in  a  tared  platinum  dish.  This  residue  consists  of  the  chlorides 
of  any  sodium  and  potassium  present. 

If  required,  the  separate  determination  of  the  two  alkali  metals  may 
be  carried  out  by  the  indirect  volumetric  method  (titration  of  the  total 
chlorine  in  a  known  weight  of  the  chlorides  ;  see  Fertilisers,  p.  135)  or  by 
the  gravimetric  method  (precipitation  of  the  potassium  as  platinichloride), 
the  procedure  being  as  described  with  fertilisers  (p.  124). 

7.  Sulphates,  Sulphides.  —  These  are  determined  as  with  limestone 
(q.v.,  Complete  Analysis,  9  and  10). 


The  deductions  to  be  drawn  from  the  composition  of  a  clay,  in  so  far  as  these 
are  of  interest  in  the  manufacture  of  cement,  are  based  (i)  on  the  proportions 
A.C.  10 


146  POZZOLANE  AND  SLAGS 

of  the  essential  components,  namely,  silica,  alumina  and  ferric  oxide  (the  sum  of 
which  is  not  less  than  80%),  in  order  that  it  may  be  calculated  in  what  ratio  it 
must  be  mixed  with  the  other  raw  materials,  and  (2)  on  the  amounts  of  lime  and 
other  impurities  which  may  be  harmful  to  the  cement. 


POZZOLANE    AND    SLAGS 

True  pozzolane  are  readily  friable,  volcanic  materials  which,  when  mixed 
with  lime,  form  mortars  capable  of  setting  even  under  water.  Their  essential 
components  are  silica,  alumina  and  ferric  oxide,  and  they  contain  also  lime, 
magnesia  and  alkalies,  together  with  a  considerable  amount  of  combined 
water.  The  more  important  and  the  best  known  are  (i)  those  from  the 
neighbourhood  of  Rome,  which  are  distinguished  as  red  (brownish  red  or 
violet  red),  black  (dark  brown  or  grey)  and  pozzolanelle  (greyish  or  reddish, 
of  more  recent  formation),  and  (2)  those  from  near  Naples,  which  are 
usually  light  grey  but  sometimes  dark  grey.  Pozzolane  are  also  found  in 
the  Auvergne  and  other  volcanic  regions.  With  the  pozzolane  are  grouped 
other  similar  materials,  such  as  santorin,  found  in  the  island  of  that  name 
and  in  other  Greek  islands,  and  trass,  which  occurs  in  the  Eifel  and  in  other 
districts  on  the  banks  of  the  Rhine  ;  both  of  these  are  greyish.  There  are 
also  non-volcanic  pozzolane,  composed  of  the  detritus  of  various  siliceous 
rocks,  but  their  use  is  somewhat  limited. 

The  name  artificial  pozzolane  is  given  to  substitutes  for  pozzolana  ; 
these  are  obtained  by  calcination  of  clay,  schist,  basalt,  etc.,  but  use  is 
made  principally  of  blast-furnace  slag,  which  is  granulated  by  pouring  it 
into  water  direct  from  the  furnace. 

The  testing  of  pozzolane  and  slags  includes  quantitative  chemical  analysis 
and,  especially  for  pozzolane,  certain  technical  tests  indicated  below. 


1.    Chemical  Analysis 

Chemical  analysis  of  pozzolane  and  slags  may  be  made  by  the  methods 
already  described  for  the  analysis  of  clays,  determinations  being  made  of 
the  moisture,  the  loss  on  ignition,  the  silica,  alumina  and  ferric  oxide  (also 
any  manganese  oxide),  lime,  magnesia,  alkalies  (also  any  sulphates  and, 
especially  in  slags,  sulphides).  As  regards  the  loss  on  ignition,  in  good 
pozzolane  this  is  composed  almost  entirely  of  the  combined  water,  since 
carbon  dioxide. is  not  usually  present  in  appreciable  quantity.  The  com- 
bined water  is  an  important  factor  with  the  pozzolane,  standing  in  close 
relation  to  their  hydraulic  properties. 

Further,  in  some  cases,  it  is  necessary  to  determine  the  constituents  of 
the  silicates  of  pozzolane  attackable  by  hydrochloric  acid  and  of  those  non- 
attackable.  In  this  event,  2-4  grams  of  the  substance  are  treated  with 
hydrochloric  acid  in  the  same  way  as  the  limestones  and  marls  (q.v.,  Com- 
plete Analysis,  6,  a).  The  undecomposed  residue  will  contain  the  sand,  the 
undecomposed  silicates  and  the  silica  of  the  silicates  which  have  been 
attacked  ;  the  bases  corresponding  with  the  last  are  found  in  the  filtrate 


POZZOLANE  AND   SLAGS  147 

and  are  determined  by  the  method  already  described  (see  Limestones,  Com- 
plete Analysis,  7  and  8).  By  treatment  of  the  insoluble  residue  with  sodium 
carbonate  (see  Limestones,  Complete  Analysis,  6,  b),  the  silica  of  the  silicates 
attacked  by  the  acid  is  separated.  The  new  residue  is  disaggregated  and 
examined  by  the  methods  given  for  clays  (q.v.,  3-6)  the  silica  and  the  differ- 
ent bases  of  the  silicates  not  decomposed  by  hydrochloric  acid  thus  being 
determined. 

Another  determination  of  use  in  the  evaluation  of  pozzolanic  materials 
is  that  of  the  constituents  of  the  silicates  attackable  by  alkalies  by  Lunge 
and  Millberg's  method.1  Pozzolana  and  trass  contain,  as  active  components, 
zeolitic  silicates,  especially  a  silicate  of  aluminium  and  sodium  analogous 
to  analcite,  these  being  decomposed  in  the  hot  by  caustic  potash.  Thus, 
by  digesting  0-5  gram  of  the  substance  with  50  c.c.  of  30%  caustic  potash 
solution  for  about  6  hours  on  the  water-bath,  diluting,  filtering  and  deter- 
mining the  silica  and  alumina  in  the  filtrate,  an  indication  is  obtained  of 
the  technical  value  of  the  material.  The  experiments  of  the  authors  men- 
tioned above  on  various  specimens  of  trass  and  pozzolana  show  that  about 
24-28%  of  silica  and  11-13%  of  alumina  pass  into  solution  under  this 
treatment. 


2.    Technical  Examination  of  Pozzolane 

This  includes  :  certain  preliminary  tests  for  detecting  the  presence  of 
heterogeneous  and  inert  material ;  the  lime  absorption  test,  and  especially 
tests  relating  to  the  fineness,  the  absolute  and  apparent  density,  the  setting 
and  the  strength. 

1 .  Presence  of  Extraneous  Matter. — The  presence  of  earthy  matters 
may  be  detected  by  shaking  the  pozzolana  with  water  and  allowing  to 
settle  :    pozzolana  free  from  earth  deposits  rapidly  and  leaves  the  liquid 
clear.     When  the  pozzolana  is  heated  with  caustic  potash  solution,  if  earthy 
matter  is  present,  the  organic  substances  of  the  latter  colour  the  potash 
solution  brown,  and  the  addition  of  acid  then  produces  a  brown  precipitate. 
Further,  on  dry  distillation,  nitrogenous  organic  matter  yields  empyreumatic 
products,  alkaline  owing  to  the  presence  of  ammonia  ;    a  pozzolana  con- 
taining them  will  give,  therefore,  ammonia  when  heated  with  caustic  potash 
solution. 

2.  Lime  Absorption. — This  test  yields  satisfactory  results  if  a  control 
test  on  a  good  pozzolana  of  known  value  is  also  made.     A  10%  sugar  solu- 
tion is  left  in  contact  with  an  excess  of  spent  lime  for  at  least  12  hours, 
with  frequent  shaking.     After  filtration,  the  alkalinity  of  the  solution  is 
determined   by  means   of  N- hydrochloric   acid,   of  which   I   c.c.  =  0-028 
gram  CaO. 

The' test  is  made  by  treating  20  grams  of  pozzolana  in  a  flask  with  100 
c.c.  of  the  above  solution,  closing  the  flask  and  leaving  it  for  two  or  three 
days,  with  occasional  shaking  ;  the  liquid  is  then  filtered  through  a  dry 
filter  and  an  aliquot  part  titrated  with  N- hydrochloric  acid.  The  quantity 
of  calcium  oxide  absorbed  by  100  grams  of  the  pozzolana  is  then  calculated. 

1  Zeitschr.  fur  angew.  Chem.,  1897,  p.  428. 


148  POZZOLANE  AND   SLAGS 

This  quantity  usually  varies  between  i  and  2  grams  and  is  greater  with 
the  better  pozzolane. 

3.  Granularity  and  Fineness. — With  pozzolane  in  the  natural  granular 
condition,  the  degree  of  granularity  is  determined  by  using  a  series  of  sieves 
with  meshes  measuring  5,  4,  3,  2,  1-5,  i  and  0-5  mm.,  2  grams  of  material 
being  taken  and  the  results  expressed  as  percentages  (of  the  total  weight) 
not  passing  through   each   sieve.     With   powdered   pozzolana,    however, 
the  fineness  of  grinding  is   determined  in   the   way  indicated  later   for 
cements. 

This  procedure,  and  also  the  ones  described  under  4,  5,  6  and  7,  are  those 
prescribed  in  the  Official  Italian  Regulations  and  Conditions,  approved  by  the 
decree  of  the  Minister  of  Public  Works,  June  13,  1911. 

4.  Specific  Gravity. — The  specific  gravity  (absolute  density)  is  deter- 
mined on  the  powdered  material,  dried  and  passed  through  a  sieve  of  900 
meshes  per  sq.  cm.,  by  the  methods  indicated  later  for  cements. 

5.  Apparent  Density. — This  is  the  weight  of  i  litre  of  the  material 
poured  without  compression.     With  granular  pozzolane  it  is  determined 
after  the  latter  has  been  dried  and  passed  through  a  sieve  with  round  orifices 
3  mm.  in  diameter,  the  same  apparatus  and  procedure  being  used  as  with 
cements,  excepting  that  the  plate  in  the  funnel  has  apertures  3  mm.  instead 
of  2  mm.  in  diameter.     With  powdered  pozzolane,  however,  the  apparent 
density  is  determined  exactly  as  with  cements.     The  result  is  expressed 
in  grams  per  litre  (or  kilos  per  cub.  m.). 

6.  Setting  Test.- — The  procedure  is  different  for  granular  or  powdered 
pozzolana. 

In  the  former  case  the  pozzolana  should  be  previously  dried  in  the  oven 
until  of  practically  constant  weight  and  then  passed  through  a  sieve  with 
circular  holes  3  mm.  in  diameter.  Common  lime  (with  at  least  95%  CaO) 
is  hydrated  by  sprinkling  it  with  water,  being  afterwards  left  for  a  fortnight 
in  a  moist  place  and  sieved  to  remove  uncombined  or  inert  particles.  A 
normal  mortar  is  then  prepared  from  i  part  of  the  powdered  slaked  lime 
and  3  parts  of  the  pozzolana  prepared  as  above  ;  the  manipulation  is  carried 
out  at  a  temperature  of  15-20°  on  a  marble  slab  by  means  of  a  trowel,  the 
components  being  mixed  at  first  dry  and  then  with  ordinary  water,  this 
being  gradually  added  until  a  homogeneous,  plastic  mass  is  obtained  which 
agglomerates  under  the  pressure  of  the  hand. 

This  mortar  is  used  to  fill  two  zinc  plate  cylindrical  moulds,  10  cm.  in 
diameter  and  5  cm.  in  height,  which  are  kept  in  a  moist  atmosphere,  the 
setting  tests  being  commenced  after  48  hours  and  repeated  every  24  hours. 
In  this  test  use  is  made  of  a  Vicat  needle  similar  to  that  described  later  for 
cements  but  with  a  total  weight  of  i  kilo  and  of  rather  different  dimensions  : 
the  point  of  the  needle  is  somewhat  conical,  the  length  being  40  mm.,  and 
the  diameter  3-2  mm.  at  the  base  and  1-66  mm.  at  the  apex.  The  needle 
is  allowed  to  fall  from  a  height  of  30  mm.,  and  hardening  is  considered  to 
begin  when  the  needle  does  not  penetrate  more  than  7  mm.  into  the  mortar. 
At  this  point,  one  of  the  mortars  is  placed  in  water  and  the  other  kept  in 
the  moist  chamber,  the  periodical  tests  being  continued  on  both  and  the 


POZZOLANE  AND   SLAGS  149 

results  given  graphically  in  a  diagram  (days  as  abscissae  and  penetration  of 
the  needle  in  mm.  as  ordinates). 

In  the  second  case,  that  is  with  powdered  pozzolane,  the  mortar  is  pre- 
pared from  i  part  of  powdered  slaked  lime  and  4  parts  of  the  pozzolana, 
these  being  mixed  first  dry  and  then  with  water ;  the  consistency 
of  the  mortar  and  the  setting  are  tested  by  methods  indicated  later  for 
cements. 

7.  Strength. — Tensile  and  compression  tests  are  carried  out  as  with 
cements. 

With  a  granular  pozzolana,  the  moulds  are  filled  by  hand  by  means  of 
a  spatula  with  the  mortar  prepared  as  for  setting  tests  ;  after  some  days, 
when  the  briquettes  have  attained  a  certain  consistency,  they  are  removed 
from  the  moulds  and  kept  first  in  the  moist  chamber  until  7  days  after 
mixing  and  subsequently  some  in  water  and  some  in  moist  air.  The  strength 
test  is  made  after  28  days  and  may  be  repeated  after  84  days,  210  days 
and  i  year. 

In  the  case  of  powdered  pozzolana,  a  normal  mortar  is  prepared  from 
t  part  of  the  lime-pozzolana  mixture  (i  of  lime  and  4  of  pozzolana)  and 
3  parts  of  normal  sand  (see  later :  Cements),  the  procedure  for  filling  the 
moulds  and  carrying  out  the  tests  being  the  same  as  for  cements. 

* 
*  * 

The  chemical  compositions  of  some  of  the  better  known  pozzolane,  santorins 
and  trass  are  given  in  Table  IV. 

Pozzolane  should  be  free  from  extraneous  and  inert  substances  and  for  the 
measurements,  both  by  weight  and  by  volume,  they  should  not  contain  more 
than  10%  of  moisture. 

Pozzolane  are  regarded  as  energetic  when,  in  the  natural  granular  state,  they 
answer  the  following  requirements  :  (i)  the  normal  mortar  (3  parts  by  weight 
of  pozzolana  to  i  of  lime),  after  7  days  in  the  moist  chamber,  does  not  allow  the 
Vicat  needle  weighing  i  kilo  to  penetrate  more  than  7  mm.  when  falling  from  a 
height  of  30  mm.  ;  (2)  after  28  days — 7  in  moist  air  and  21  in  water — the  briquettes 
of  normal  mortar  exhibit  a  tensile  strength  of  not  less  than  4  kilos  per  sq.  cm. 
and  a  compression  strength  of  at  least  20  kilos  per  sq.  cm. 

Feeble  pozzolane  are  those  yielding  normal  mortars  which  do  not  attain 
the  above  strength  but  allow,  after  7  days,  the  needle  to  penetrate  not  more  than 
10  mm.,  and  after  28  days  exhibit  tensile  and  compressive  strengths  of  2  and  10 
kilos  per  sq.  cm.  respectively.  If  these  standards  are  not  attained,  the  material 
is  not  regarded  as  pozzolanic  in  character. 

Slags,  to  be  of  use  in  the  cement  industry,  should  be  basic,  that  is,  the  ratio 
CaO  :  SiO2  should  be  not  less  than  i,  and  they  should  be  as  rich  as  possible  in 
alumina  and  as  poor  as  possible  in  manganese,  magnesia  and  sulphides.  The 
composition  of  a  good  slag  should  lie  between  the  limits  :  SiO2,  25-36%  ;  A12O3, 
10-22%  ;  Fe2O3,  up  to  1-5%  ;  FeO,  up  to  2%  ;  MnO,  up  to  3%  ;  CaO,  30-50%  ; 
MgO,  up  to  3%  ;  CaSO4,  up  to  2%  ;  and  CaS,  up  to  3%.  Alkalies  are  usually 
present  in  small  quantity. 


150 


POZZOLANE  AND   SLAGS 


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LIME  151 


LIME 

This  is  the  product  of  the  calcination  of  limestone  and,  when  mixed  with 
siliceous  sand,  forms  the  well-known  common  mortar.  Limes  are  distin- 
guished as  fat  limes,  consisting  essentially  of  calcium  oxide  and  readily 
slaked  with  evolution  of  considerable  heat  and  with  increase  of  volume, 
and  poor  limes,  containing  marked  quantities  of  clay,  magnesia  and  other 
impurities. 

The  chemical  analysis  of  lime  is  analogous  to  that  of: limestone  (see 
Limestones  and  Marls),  but  usually  the  determination  of  carbon  dioxide 
is  unnecessary.  For  industrial  purposes,  however,  certain  technical  tests 
generally  suffice,  these  being  principally : 

1.  Ease  of  Storage. — This  is  deduced  from  the  greater  or  less  time 
required  for  a  lime  exposed  to  the  air  to  become  slaked  and  fall  into  powder 
in  contact  with  the  moisture  of  the  air. 

2.  Ease  of  Slaking.— This  is  ascertained  by  observing  if  the  lime, 
mixed  with  3-4  times  its  weight  of  water,  undergoes  hydration  in  a  "short 
time  with  pronounced  generation  of  heat  and  formation  of  a  dense  paste. 

3.  Volume   after    Slaking. — This   is  '  determined   by   means   of   the 
Michaelis  volumenometer,  consisting  of  a  brass  vessel  into  the  orifice  of 
which  a  glass  tube  with  graduations  starting  from  200  c.c.  may  be  screwed 
air-tight.     In  the  container  a  piece  of  the  lime  weighing  25-50  grams  is 
slaked  with  the  amount  of  water  necessary  to  obtain  a  dense  paste,  heat 
being  applied,  where  necessary,  by  a  water-bath  and  also  occasional  stirring 
until  cracks  begin  to  develop  in  the  paste.     The  latter  is  then  allowed  to 
cool,   the  graduated  tube  fitted,   200   c.c.    of  water    introduced   from  a 
pipette,  and  the  volume  read. 

Another  method,  based  on  the  use  of  a  porous  cylinder  and  capable  of 
giving  good  results,  has  been  described  by  G.  Giorgis  and  G.  Cenni.1 

In  practice,  owing  to  the  difficulty  of  obtaining  a  small  sample  repre- 
senting the  bulk  of  a  lump  lime,  a  large  quantity  of  the  substance  (at  least 
5  kilos)  is  sprinkled  with  water,  left  in  the  air  for  at  least  two  days,  after 
which  water  is  added  to  give  a  paste  which  can  be  poured,  this  being  then 
introduced  (through  a  sieve  to  retain  inert  matter)  into  a  bucket  of  known 
dimensions  ;  after  the  excess  of  water  has  been  separated  from  the  surface 
of  the  paste,  the  level  of  the  latter  is  read  off  and  its  volume  calculated. 

*  * 

Fat  lime  for  the  production  of  mortar  should  be  of  recent  and  thorough  kiln- 
ing, and  not  powdery  or  effloresced  ;  it  usually  contains  not  less  than  95%  CaO, 
mostly  free.  It  should  be  non- vitreous  and  of  uniform  colour,  and  when  mixed 
with  the  necessary  quantity  of  water  it  should  undergo  rapid  slaking  with  trans- 
formation into  a  firm  paste,  without  leaving  any  appreciable  residue  due  to  insuf- 
ficiently burnt,  siliceous  or  otherwise  inert  matter  ;  the  yield  is  usually  not  less 
than  2-5  cub.  dm.  of  paste  per  kilo  of  quicklime. 

1  Annali  di  Chim.  applicata,   1915,  III,  p.   175. 


152  HYDRAULIC  LIMES  AND  CEMENTS 

HYDRAULIC    LIMES    AND    CEMENTS 

The  chief  of  these  products  are  furnished  by  the  kilning  of  argillaceous 
limestone  or  marl  or  mixtures  of  these  with  each  other  or  with  clay.  Among 
them  are  :  Hydraulic  lime,  which  is  whitish  or  yellowish  and  causes  sneezing 
when  its  powder  is  diffused  sparsely  in  the  air  ;  natural  rapid-setting  cement 
or  Roman  cement,  dark  yellow  or  greyish  yellow  ;  natural  slow-setting  cement 
or  natural  Portland  cement,  and  artificial  (or  true]  Portland  cement,  dark 
grey,  often  inclining  to  greenish.  Other  forms  of  cement  are  Grappier's 
cement,  made  from  the  argillaceous  residues  from  the  slaking  of  hydraulic 
lime,  and  of  whitish  colour  ;  slag  cements,  intimate  mixtures  of  blast-furnace 
slag  with  lime,  grey  in  colour,  and  mixed  cements. 

The  testing  of  these  products  includes  chemical  analysis  and,  what  is 
of  greater  practical  importance,  certain  technical  tests  described  later. 

1.    Chemical  Analysis 

The  more  important  determinations  to  be  made  with  hydraulic  limes 
and  with  cements  are  :  loss  on  ignition  (water  plus  carbon  dioxide),  total 
silica,  alumina  plus  ferric  oxide,  lime  and  magnesia.  In  some  cases  esti- 
mations are  required  of  the  carbon  dioxide,  the  sand  separately  from  the 
combined  silica,  ferric  oxide  separately  from  alumina,  sulphates  (gypsum) 
and,  in  slag  cements,  sulphides  (calcium  sulphide) .  All  these  determinations 
are  made  by  the  methods  already  described  in  considering  limestones  and 
marls. 

Sometimes,  in  order  to  detect  the  presence  of  heterogeneous  materials 
(e.g.,  of  slag  in  a  Portland  cement),  it  is  convenient  to  analyse  separately 
the  finer  parts  (passing  through  a  sieve  with  4,900  meshes  per  sq.  cm.)  and 
the  coarser  ones  :  any  appreciable  difference  indicates  addition  of  extraneous 
material. 

To  the  determinations  mentioned  above,  that  of  the  alkalinity  (free 
lime),  carried  out  as  follows,  is  sometimes  added  :  i  gram  of  the  finely 
powdered  material  is  shaken  for  10  minutes  with  100  c.c.  of  distilled  water 
and  filtered,  50  c.c.  of  the  filtrate  being  titrated  with  N/io-hydrochloric 
acid. 

From  the  results  of  the  chemical  analysis  it  is  usual  to  calculate  the 
relations  between  the  principal  components.  The  hydraulic  index  is  the 
ratio,  (silica  +  alumina)  :  lime  ;  according  to  some,  the  ferric  oxide  also 
is  added  to  the  alumina,  while,  according  to  others,  the  magnesia  should 
be  added  to  the  lime,  owing  to  analogous  functions  in  the  setting.  The 
hydraulic  modulus  of  Michaelis  is  the  inverse  ratio,  namely,  lime  :  (silica  -f 
alumina  +  ferric  oxide). 

2.    Technical  Tests 

The  chief  of  these  are  as  follows  : 

1.  Ocular  Examination. — This  is  made  with  a  lens  and  may  detect 
the  presence  of  extraneous  matter,  such  as  particles  of  coal,  sand,  sing, 
gypsum,  etc. 


HYDRAULIC  LIMES  AND  CEMENTS  153 

2.  Methylene  Iodide  Test. — This  serves  to  separate  the  extraneous 
matters  accompanying  a  cement  and  is -based  on  their  different  densities. 
It  applies  especially  to  Portland  cement  and  is  carried  out  by  shaking  a 
small  quantity  of  the  cement  with  a  solution  of  methylene  iodide  in  benzene 
or  oil  of  turpentine  of  density  3  *  and  allowing  to  stand.    The  cement 
particles  are  the  heavier  and  settle,  whilst  the  extraneous  matters  float. 

When  a  more  complete  separation  is  required,  methylene  iodide  solu- 
tions of  densities  3-05,  3-00,  2-95  and  2-70  are  successively  used.  What 
sinks  in  the  first  solution  consists  of  pure  Portland  cement  ;  that  of  density 
between  3  and  3-05  is  not  quite  pure  cement,  that  between  2-95  and  3 
is  mixed  cement  and  slag,  and  that  between  2-70  and  2-95  pure  slag  ; 
that  floating  in  the  solution  of  density  2-70  may  be  coal,  ash,  gypsum,  and 
the  like.  The  separate  fractions  may  be  examined  to  ascertain  their  nature. 

3.  Specific  Gravity. — This  may  be  determined  with  the  picnometer, 
using  benzene  or  benzine  as  liquid.     Use  is  also  largely  made  of  Schumann's 
volumenometer,  which  consists  of  a  bottle,  in  the  neck  of  which  is  ground 
a  glass  tube  graduated  in  tenths  of  a  c.c.     The  bottle  is  filled  with  the 
benzene  or  benzine  to  the  commencement  of  the  graduation  and  the  division 
to  which  the  liquid  reaches  read  ;   TOO  grams  of  cement  (or  lime)  are  then 
introduced  into  the  bottle,  which  is  tapped  gently  to  make  the  air-bubbles 
rise,  the  new  level  of  the  liquid  being  then  read. 

A  more  convenient  volumenometer  is  that  of  Le  Chatelier,  which  com- 
prises a  bulb  of  about  120  c.c.  capacity,  terminated  by  a  neck  0-20  metre 
high  with  an  expansion  measuring  exactly  20  c.c.  between  two  marks  ; 
above  the  upper  mark  the  tube  is  graduated  from  o  to  3  c.c.  in  tenths. 
When  the  apparatus  is  full  of  benzene  to  the  lower  mark,  a  definite  weight 
of  the  cement  (64  grams  of  Portland  cement  may  be  used  or  60  grams  or 
less  of  a  lighter  product)  is  introduced  by  means  of  a  funnel  reaching  just 
below  the  upper  mark.  The  increase  in  volume  represents  the  volume 
occupied  by  the  cement. 

According  to  the  Official  Italian  Regulations  and  Conditions, 2  the  specific 
gravity  (absolute  density)  of  hydraulic  agglomerants  may  be  determined  by 
any  method  provided  it  allows  of  an  accuracy  of  two  units  in  the  second  decimal 
figure  ;  it  should  be  determined  on  the  material  after  previous  drying  and  powder- 
ing so  as  to  pass  through  a  sieve  of  900  meshes  per  sq.  cm.,  and  the  temperature 
of  the  apparatus,  material  and  liquid  during  the  determination  should  be 
about  15°. 

4.  Apparent  Density. — This  is  the  weight  of  a  litre  of  the  material 
poured  without  compressing.     To  determine  it,  the  cement  is  gradually 
introduced  through  a  funnel  into  a  litre  cylinder  10  cm.  high  until  the 
cylinder  is  not  only  completely  filled  but  heaped  up.     The  excess  is  then 
removed  by  drawing  a  straight  strip,  held  vertically,  across  the  top  of  the 
cylinder,  which  is  then  weighed.    The  weight  thus  found,  less  the  tare, 
gives  the  apparent  density. 

According  to  the  Official  Regulations  (Italian)  already  mentioned,  the  funnel 
to  be  used  for  filling  the  cylinder  is  20  mm.  in  diameter  at  the  base  and  150  mm. 

1  The  density  of  methylene  iodide  is  3-33  at  the  ordinary  temperature. 

2  Approved  by  the  decree  of  the  Minister  of  Public  Works,  January  10,  1907. 


154 


HYDRAULIC  LIMES  AND  CEMENTS 


at  a  point  150  mm.  above  the  base  ;  at  this  height  is  fixed  a  perforated  disc' 
with  about  1050  holes  2  mm.  in  diameter  per  sq.  dm.  The  funnel  is  prolonged 
into  a  cylindrical  tube  20  mm.  in  diameter  and  100  mm.  long,  the  lower  extremity 
being  50  mm.  from  the  top  of  the  cylinder  beneath.  The  material  to  be  tested 
is  poured  on  to  the  perforated  disc  in  quantities  of  about  300  grams  at  a  time, 
and  is  stirred  with  a  wooden  spatula  40  mm.  wide  to  assist  the  passage  through 
the  holes.  During  the  filling  care  must  be  taken  not  to  shake  the  apparatus.. 
The  mean  of  three  consecutive  results  is  taken  as  the  true  value. 

Some  authorities  advise  determination  of  the  litre-weight  of  the  cement 
when  compressed  by  a  definite  number  of  blows  (generally  1000). 

5.  Fineness  of  Grinding. — This  is  determined  by  sieving  the  material 
through  successive  metal  wire  sieves  and  weighing  the  residue  on  each  sieve. 
Use  is  generally  made  of  sieves  of  900-4900  meshes  per  sq.  cm.,  made  of 
Wires  of  diameter  0-15  and  0-05  mm.  respectively.      The  test  is  made  on  a 
50  gram  sample,  the  results  as  percentages  being  obtained  by  adding  two 
results  obtained  with  the  same  sieve.     The  sieving  is  conducted  by  hand, 
and  is  regarded  as  complete  when  25  successive  shakings  do  not  cause  more 
than  o-i  gram  of  material  to   pass  through   the   sieve.      The  results   are 
expressed  by  adding,  for  each  sieve,  the  weights  of  the  residues  not  able 
to  pass  through  it. 

6.  Quantity   of   Water   for   Pasting    (gauging) — The   quantity  of 

water  required  to  give  a  paste  of  normal 
consistency  (normal  paste)  is  measured  as 
follows  :  400  grams  of  the  material  are 
placed  on  a  marble  or  zinc  slab  in  the 
form  of  a  heap  hollowed  in  the  middle. 
Into  this  is  poured,  in  one  lot,  the  whole  of 
the  water  considered  necessary  at  15-20°, 
the  whole  being  mixed  rapidly  with  a 
trowel,  for  one  minute  with  a  rapid-setting 
cement  or  for  three  minutes  with  a  slow- 
setting  cement  or  a  hydraulic  lime  (in  any 
case  for  a  less  time  than  is  required  for 
setting  to  begin  :  see  below). 

With  the  same  trowel  the 
paste  is  immediately  filled  into  a 
split  cylindrical  metal  or  ebonite 
mould,  4  cm.  high  and  8  cm.  in 
diameter  on  a  smooth  glass  plate  ; 
FIG.  8  the  surface  of  the  cement  is. 

smoothed  with   the   trowel,  care 

being  taken  to  avoid  compression.  The  Tetmajer  rammer  is  then  allowed 
to  descend  into  the  mortar  by  its  own  weight  (300  grams).  This  rammer 
consists  of  a  small  cylinder,  i  cm.  in  diameter,  which  replaces  the  needle 
of  the  Vicat  apparatus  (Fig.  8).  The  consistency  is  normal  when  the 
cylinder  comes  to  rest  with  its  base  about  6  mm.  from  the  level  of  the  glass 
plate,  as  indicated  on  the  scale.  If  the  consistency  is  not  normal,  the  test 
is  repeated  with  a  different  quantity  of  water.  The  proper  amount  of 
water  used  is  divided  by  4  to  give  the  quantity  per  100  grams  of  material. 


HYDRAULIC  LIMES  AND  CEMENTS  155 

7.  Setting  Time. — This  is  determined  on  the  normal  paste,  and  that 
used  in  the  preceding  test  may  be  used,  being  kept  during  the  whole  of 
the  tests  in  a  moist  chamber  at  about  15°.    The  test  is  made  with  Vicat's 
needle  (Fig.  8),  which  is  a  cylindrical  steel  needle  of  i  sq.  mm.  section  (1-13 
mm.  diameter),  cut  normally  to  the  length  and  weighing,  with  the  rest  of 
the  moving  parts,  300  grams.     It  is  brought  gently  into  contact  with  the 
mortar  to  ascertain  if  it  penetrates.     The  test  is  repeated  at  first  every 
minute  and  afterwards  at  gradually  increasing  intervals.     The  initial  set 
is  taken  as  the  time  when  the  needle  fails  to  reach  the  bottom  of  the  test- 
piece  and  the  final  set  as  that  when  the  needle  fails  to  enter  to  an  appreciable 
extent  (about  o-i  mm.)  ;   times  are  measured  from  the  moment  when  the 
water  is  added  to  the  cement  for  the  gauging. 

This  procedure  is  that  adopted  by  the  Official  Italian  Regulations.  When 
setting  is  almost  complete,  it  is  well  to  detach  the  mould  from  the  glass  and  test 
on  the  lower  surface  of  the  mortar  where  it  is  more  polished  and  homogeneous  ; 
with  slow  setting,  it  is  useful  to  cover  the  mould  with  a  glass  to  prevent  drying. 
Some  advise,  especially  with  very  slow-setting  products,  the  determination  of 
the  time  of  setting  under  water. 

The  rise  of  temperature  of  the  mortar  during  setting  may  give  useful  indica- 
tions and  is  ascertained  by  means  of  a  thermometer  with  its  bulb  immersed 
in  the  paste  ;  temperature  readings  are  taken  at  regular  intervals  and  the  tem- 
perature-time curve  traced. 

8.  Strength. — Only  a  brief  reference  will  be  made  to  these  mechanical 
tests,  which  are  not  usually  made  in  chemical  laboratories.     Chief  among 
them  are  those  of  tensile  and  compression  strengths. 

According  to  the  Official  Italian  Regulations,  such  tests  are  made  in 
some  cases  on  a  normal  paste  of  the  pure  cement  (see  above,  6),  but  usually 
on  a  normal  mortar  obtained  by  making  an  intimate  mixture  of  i  part  of 
the  agglomerating  material  with  3  parts  of  sand  and  preparing  a  paste 
from  this  and  the  necessary  amount  of  water,  to  be  determined  by  trial 
(usually  about  8%  by  weight  of  the  mixture).  The  granules  of  the  normal 
sand  to  be  used  must  pass  through  circular  holes  1-5  mm.  in  diameter  but 
not  through  i  mm.  holes. 

For  tensile  measurements  briquettes  are  moulded  in  the  shape  of  the 
figure  8  and  of  definite  form  and  dimensions,  the  minimum  section  in  the 
narrowest  part  being  5  sq.  cm.  The  mortar  is  compressed  into  the  mould 
by  120  blows,  delivered  during  3  minutes,  of  a  hammer  weighing  2  kilos 
falling  from  a  height  of  0-25  metre  and  developing  energy  amounting  to 
o-30-kilogram-metre  per  gram  of  dry  substance.  The  briquette  is  then 
removed  from  the  mould.  The  tests  are  usually  made  after  28  days  (or  7 
with  rapid-setting  cements),  during  the  first  of  which  (or  the  first  two  with 
hydraulic  limes)  the  briquettes  are  kept  in  moist  air  and  during  the  remainder 
in  water.  In  some  cases  measurements  are  made  after  different  periods 
(in  general,  the  strength  after  28  days  is  about  two-thirds  of  the  value  after 
i  year).  The  results  are  expressed  in  kilos  per  sq.  cm.  of  the  minimal 
section  and  for  a  given  material  six  briquettes  are  tested  and  the  mean  of 
the  four  highest  results  taken. 

With  pure  cement,  the  briquettes  are  made  by  hand  with  the  help  of 


156  HYDRAULIC  LIMES  AND  CEMENTS 

a  trowel  and  are  taken  from  the  moulds  after  24  hours,  when  they  are 
immersed  in  water. 

Greater  value  attaches  to  the  results  of  compression  tests.  According 
to  the  Italian  Regulations,  cubical  briquettes  of  50  sq.  cm.  face  are  made 
in  suitable  moulds  by  compressing  with  160  blows  from  a  3  kilo  hammer 
falling  0-5  metre  and  developing  0-30  kilogram-metre  per  gram  of  dry  sub- 
stance. The  briquettes  are  kept  and  the  results  expressed  as  with  tensile 
strength,  the  same  being  the  case  with  briquettes  of  pure  cement.  The 
compressive  stress  should  be  exerted  on  two  opposite  faces  which  have  been 
in  contact  with  lateral  walls  of  the  mould. 

Bending  tests  are  also  sometimes  made,  and  for  practical  purposes,  tests 
of  the  indeformability  or  constancy  of  volume  in  the  cold  and  in  the  hot  are 
of  importance.  Further,  in  some  cases,  it  may  be  advisable  to  make  tests 
of  adhesion,  porosity  and  permeability.  For  these  tests  and  for  greater 
details  of  the  compression  and  tension  tests,  reference  must  be  made  to 
special  treatises. 

*  * 

Hydraulic  limes  have  the  specific  gravity  2-5-2-9  or,  more  commonly,  2.7- 
2 '85,  and  their  apparent  density  is  usually  0-5-0 -8,  and  may  be  even  greater  with 
those  having  very  marked  hydraulic  properties.  The  chemical  composition 
varies  somewhat,  but  in  ordinary  cases  the  proportion  of  clay  is  20-30%.  The 
hydraulic  index  may  vary  between  fairly  wide  limits,  but  in  most  instances  is 
less  than  0-50.  The  loss  on  calcination  is  usually  8-12%  but  may  reach  20% 
or  more  ;  as  regards  alkalinity,  the  solution  obtained  from  0*5  gram  of  substance 
requires  about  20  c.c.  of  N/io-acid.  For  a  paste  of  normal  consistency,  hydraulic 
limes  almost  always  require  more  than  40%  and  sometimes  even  60%  of  water  ; 
setting,  in  either  air  or  water,  seldom  takes  place  in  less  than  a  day,  and  often 
takes  longer. 

According  to  the  Official  Italian  Regulations,  hydraulic  lime  should  have  a 
specific  gravity  of  at  least  2-7  and  should  not  leave  more  than  7%  of  residue 
on  a  sieve  of  900  holes  per  sq.  cm.  and  not  more  than  25%  on  one  of  4900  holes  ; 
the  setting  of  the  normal  paste  should  not  begin  earlier  than  6  hours  and  should 
not  end  later  than  48  hours.  The  strength  of  the  normal  mortar  briquette  after 
28  days  should  not  be  less  than  :  tension,  5  kilos  per  sq.  cm.  for  ordinary  hydraulic 
lime  and  8  for  those  with  marked  hydraulic  qualities  ;  compression,  25  kilos 
and  50  kilos  per  sq.  cm.  respectively. 

Natural  cements  usually  have  the  specific  gravity,  2-8-3,  and  the  apparent 
density  0-7-1  for  quick-setting,  and  sometimes  as  much  as  1-2  for  slow-setting 
cements.  The  hydraulic  index  is  usually  0-50-0-80  or  more,  and  is  greater  with 
quick-setting  than  with  slow-setting  products  (with  the  former,  the  Michaelis 
hydraulic  modulus  is  generally  1-2-1-6).  The  loss  on  ignition  and  the  alkalinity 
are  almost  always  less  than  with  the  hydraulic  limes.  At  the  most  30-45% 
of  water  is  required  for  the  normal  paste  and  setting  requires  less  than  half  an 
hour  for  quick- setting  and  more  than  half  an  hour — sometimes  some  hours — 
for  rapid-setting  cements.  Semi-slow-setting  cements  are  sometimes  regarded 
as  an  intermediate  grade,  but  the  transition  from  rapid-  to  slow-setting  cements 
is  too  gradual  to  allow  of  the  definition  of  the  limits  of  such  a  class. 

For  rapid-setting  cements  the  Official  Italian  Regulations  prescribe  :  a  specific 
gravity  greater  than  2-8  ;  not  more  than  20%  of  residue  on  a  900  mesh  sieve  ; 
initial  and  final  sets  to  occur  between  i  minute  and  30  minutes  ;  briquettes  of 
normal  paste  to  exhibit,  after  7  days,  tensile  and  compressive  strengths  not  less 
than  1 6  and  160  kilos  respectively  per  sq.  cm. 

True  Portland  cement  has  the  specific  gravity  3-05-3-25  and  the  apparent 


GYPSUM  157 

density  1-1-1-3  or>  after  compression  caused  by  1000  shakes,  about  1-8.  The 
chemical  composition  is  moderately  constant ;  the  loss  on  ignition  never  reaches 
5%  and  usually  does  not  exceed  3%  ;  the  alkalinity  is  somewhat  less  than  in 
limes,  only  4-6  c.c.  of  N/io-acid  being  required  per  0-5  gram  of  substance. 
The  essential  components  usually  vary  between  the  following  limits  : 

Silica 19-26% 

Alumina  .........       4-10 

Ferric  oxide      ........       2-4 

Lime 57~67 

The  hydraulic  index  usually  lies  between  0-42  and  0-50  but  may  reach  0-60, 
and  the  Michaelis  hydraulic  modulus  varies  between  1-7  and  2-2,  its  mean  value 
being  about  2.  According  to  Le  Chatelier,  the  proportion  of  lime  should  be 
such  that,  when  the  components  are  expressed  in  chemical  equivalents,  the  ratio 

C*0  +  Mg°       is  less  than  3,  and  _         CaO  +  MgO 
Si02  +  A1203  Si02  -  (A1203  +  Fe203)1S  gre' 

As  regards  the  accessory  components,  good  Portland  cement  should  not 
contain  more  than  3%  of  MgO  or  1-2%  of  SO3,  or  sulphides  in  appreciable  quan- 
tity. This  cement  requires  27-30%  of  water  for  gauging  and  usually  sets  in  a 
few  hours. 

The  Official  Italian  Regulations  prescribe  for  Portland  cements  :  specific 
gravity  not  less  than  3-05  ;  not  more  than  2  (or  20)%  of  residue  to  remain  on  a 
sieve  of  900  (4900)  meshes  per  sq.  cm.  ;  initial  set  of  the  normal  paste  to  occur 
later  than  i  hour  and  final  set  between  5  and  12  hours  ;  after  28  days,  the  strength 
of  the  normal  mortar  briquettes  to  be  not  less  than  20  and  220  kilos  respectively 
per  sq.  cm.  towards  tension  and  compression. 

Slag  cements  have  an  apparent  density  usually  less  than  i  and  a  specific  gravity 
2-6-2-8,  the  values  for  Grappier's  cements  being  o-8-i-i  and  2-8-3  '•  mixed  cements 
approach  one  or  the  other  class,  according  to  their  composition.  All  these 
cements  require  30-40  %  of  water  and  set  after  some  hours,  almost  always  before 
24  hours.  As  regards  their  chemical  composition,  slag  cements  contain  calcium 
sulphide  in  appreciable  amount,  which  may  reach  or  surpass  3-4%,  and  they 
are  usually  richer  in  alumina  and  poorer  in  lime  than  Portland  cements.  Grap- 
pier's cements  are,  however,  poor  in  alumina  and  rich  in  silica,  of  which  they 
contain  22-30%  ;  the  loss  on  ignition  is  generally  less  than  with  hydraulic 
limes  and  mostly  about  5%.  Another  characteristic  of  Grappier's  and  slag 
cements  is  the  fineness  of  grinding  :  they  leave  almost  no  residue  on  the  900- 
mesh  sieve  and  usually  not  more  than  10%  on  the  49oo-mesh. 

Mention  must  be  made  of  the  so-called  sand  cements,  which  are  used,  especi- 
ally in  America,  for  street  paving,  dykes,  aqueducts  and  canals,  and  have  recently 
been  introduced  into  Italy.  They  consist  of  intimate  mixtures  of  Portland 
cement  and  siliceous  rock  (sand,  arenaceous  deposit,  granite,  etc.)  which  are 
ground  together  and  are  moderately  rich  in  silica  and  unattackable  silicates 
(42%  or  more). 

Tables  V,  VI  and  VII  contain  examples  of  the  compositions  and  properties 
of  hydraulic  limes  and  cements. 


GYPSUM 

Ordinary  gypsum  is  obtained  by  heating  hydrated  calcium  sulphate  at 
a  moderate  temperature  and  is  composed  essentially  of  calcium  sulphate 
still  containing  a  part  (about  one-fourth)  of  the  water  of  crystallisation. 
The  principal  impurities  which  may  be  present  are  clay,  oxide  of  iron, 
calcium  carbonate,  sand,  and  sometimes  pyrites  and  bituminous  matter. 


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160 


GYPSUM  161 

In  less  common  use  is  gypsum  for  plastering  or  for  slow-setting  ;  this, 
having  been  heated  at  a  very  high  temperature,  has  lost  almost  all  its  water. 
It  may  contain  also  calcium  hydroxide  (instead  of  carbonate)  and  calcium 
sulphide  (from  the  reduction  of  the  sulphate). 

Complete  examination  of  gypsum  includes  chemical  analysis  and  various 
physical  and  mechanical  tests  ;  in  practice,  these  are  mostly  reduced  to 
the  determination  of  the  water  and  the  setting  test. 

1 .  Chemical  Analysis  .—The  water  is  determined  by  heating  a  weighed 
quantity  of  the  sample  at  160-180°  to  constant  weight. 

In  general  the  impurities  may  be  estimated  together  with  sufficient 
accuracy  by  exhausting  a  given  weight  of  the  substance  with  hot  water 
until  all  the  calcium  sulphate  is  dissolved  and  weighing  the  residue  after 
drying. 

When  complete  analysis  is  required,  exactly  1-2  grams  are  dissolved 
in  boiling,  concentrated  hydrochloric  acid,  the  liquid  being  then  diluted 
with  boiling  water,  heated  for  a  few  minutes  longer  and  filtered,  and  the 
insoluble  residue  ignited  and  weighed.  In  an  aliquot  part  of  the  filtrate 
the  sulphuric  acid  is  determined  by  precipitation  with  barium  chloride, 
and  in  another  the  alumina  and  ferric  oxide,  lime  and  magnesia  are  succes- 
sively precipitated,  as  with  limestone.  If  required,  the  carbon  dioxide 
may  also  be  determined. 

2.  Technical   Tests. — These  consist  especially  in  determinations  of 
the  specific  gravity,  apparent  density,  fineness  of  grinding,  amount  of  water 
required  for  mixing,  time  of  setting  and  strength  ;    they  are  made  as  with 
cements. 

Properly  burnt  gypsum,  contains  about  5-7-5%  (on  the  average,  6-5%)  of 
water  and  has  the  specific  gravity  2-5-2-7  (usually  about  2-68),  whereas  slow- 
setting  and  almost  anhydrous  gypsum  has  the  specific  gravity  2-7-2-95  (usually 
2-93).  The  proportion  of  calcium  sulphate  varies  from  80  to  95%.  Unless 
present  in  large  quantities,  the  impurities  have  no  injurious  influence  on  the 
hardening.  Ordinary  gypsum  sets  in  a  few  minutes,  whilst  the  slow-setting  form 
takes  several  hours. 


A.C.  11 


CHAPTER  V 
METALS    AND    ALLOYS 

This  chapter  contains  methods  for  the  analysis  of  the  commoner  metals 
and  of  the  more  important  metallic  alloys. 

It  begins  with  the  treatment  of  ferrous  products,  descriptions  being 
given  of  the  principal  determinations  usually  made  on  cast-iron  and  malle- 
able iron  ;  special  ferrous  products  (special  steels,  ferro-metallic  alloys) 
are  then  considered.  Subsequently,  after  a  short  account  of  electrolytic 
analysis,  the  other  common  metals  are  dealt  with  :  copper,  zinc,  lead, 
antimony,  tin,  nickel,  aluminium,  silver  and  gold,  and  their  chief  alloys. 
Lastly,  methods  are  given  for  the  identification  of  some  of  the  metallic 
coatings  often  applied  to  the  surface  of  metallic  objects  for  purposes  of 
embellishment  or  protection  (gilding,  silver-plating,  nickel-plating,  etc., 
and  oxidation). 

IRON 

Metallurgical  iron  products  usually  contain,  in  addition  to  iron,  larger 
or  smaller  proportions  of  other  elements  (carbon,  silicon,  manganese,  phos- 
phorus, sulphur,  arsenic,  etc.),  which  exert  a  profound  influence  on  the 
properties.  Of  these  elements,  the  one  of  greatest  interest  is  carbon,  because, 
although  it  is  not  always  possible  to  make  clear  and  exact  distinctions,  it 
is  on  the  carbon  content  and  the  state  in  which  it  occurs — combined  or 
otherwise — that  the  distinction  and  classification  of  iron  products  are 
based. 

According  to  the  percentage  of  carbon,  these  products  are  divided  into 
two  large  classes  :  cast-iron  and  wr ought-iron. 

The  condition  of  the  carbon  determines  the  subdivision  of  cast-iron  into 
grey  and  white,  the  carbon  being  mostly  free  or  as  graphitic  carbon  in  the 
former  and  in  combination  in  the  latter. 

A  third,  intermediate  type,  of  little  importance,  is  mottled  cast-iron, 
which  is  a  white  cast-iron  containing  nuclei  of  the  grey  form. 

According  to  its  carbon  content,  malleable  iron  is  subdivided  into  wrought- 
iron  and  steel.  In  practice,  however,  the  distinction  between  iron  and 
steel  is  based,  besides  on  the  carbon  content,  on  various  other  properties, 
such  as  the  possibility  of  tempering,  the  strength,  the  microscopic  structure, 
etc.  Here,  too,  sharp  differentiation  is  impossible,  because  the  transition 
from  one  type  to  the  other  is  gradual,  while  the  presence  of  small  proportions 

162 


IRON  163 

of  extraneous  substances  (tungsten,  chromium,  silicon,  etc.)  may  exert  a 
function  analogous  to  that  of  carbon. 

Of  special  technical  interest  are  arsenic,  phosphoms,  sulphur,  etc.,  which 
are  almost  always  present  in  small  amounts  in  ferrous  products,  and  should 
therefore  be  determined,  both  in  the  crude  products  to  decide  methods  of 
refining,  and  also  in  the  refined  products  to  ascertain  if  they  are  suitable 
for  the  required  purpose. 

Complete  study  of  these  products  includes,  then,  besides  exact  chemical 
analysis,  microscopical  analysis  and  mechanical  tests  (resistance  to  tension, 
shock,  crushing,  and  elasticity  and  torsion  tests,  etc.). 

The  chemical  analysis  comprises  especially  determinations  of  the  carbon 
(total,  graphitic  and  combined),  silicon,  manganese,  phosphorus,  sulphur 
and  arsenic,  the  methods  employed  being  described  later.  In  rare  cases, 
other  determinations,  such  as  those  of  copper,  tin,  antimony  and  oxygen, 
are  required. 

In  every  case,  the  sampling  is  of  prime  importance. 

Sampling. — To  obtain  a  representative  sample,  the  whole  mass  of  the 
metal  should  be  bored  with  a  small  drill  free  from  oil,  the  greatest  cleanli- 
ness being  observed,  and  the  drillings  caught  on  a  sheet  of  brass  or  collected 
with  a  magnet.  The  whole  mass  should  be  drilled  where  possible,  as  some 
products,  notably  steels,  differ  appreciably  in  composition  inside  and  outside. 

With  large  ingots,  samples  should  be  taken  at  the  two  ends  and  the 
middle,  at  the  surface  and  interior,  and,  if  it  is  of  no  interest  to  investigate 
different  points  of  the  mass,  a  single,  homogeneous  sample  is  made  of  all 
the  borings. 

Small  objects  of  wrought-iron,  cast-iron  or  untempered  steel  may  be 
sampled  by  means  of  a  good  steel  file,  cleaned  with  ether  and  benzene,  the 
object  being  attacked  at  different  points.  Tempered  steel  must  be  softened 
by  heating  it  in  a  porcelain  crucible  unglazed  inside  placed  in  a  larger  crucible 
of  refractory  material. 

For  very  hard  products,  specially  hard  steel  drills  may  be  used.  Failing 
this,  parts  of  the  object  may  be  broken  on  an  anvil  with  a  heavy  hammer 
and  the  small  pieces  powdered  in  an  agate  mortar,  the  finer  material  being 
sieved  away  and  the  coarse  repowdered. 

1.    Determination  of  the  Carbon 

Carbon  may  occur  in  ferrous  products  in  four  forms  : 

(a)  Graphitic  carbon,  consisting  of  fragments  of  graphite  disseminated 
through  the  mass  of  the  metal  and  insoluble  in  acids. 

(b)  Annealing  carbon,  consisting  of  amorphous  graphite,  also  insoluble 
in  acids. 

(c)  Carbon  combined  as  iron  carbide,  or  carbide  carbon,  soluble  in  hot 
nitric  acid  to  a  brown  solution. 

(d)  Hardening  carbon,  contained  especially  in  steel,  and  also  in  white 
cast-iron,  and  liberated  as  gaseous  products  during  the  action  of  hot  nitric 
acid. 

Methods  are  given  below  admitting  of  the  determination  of  the  total 


1 64 


IRON 


carbon  (a  -f-  b  +  c  +  d),  the  graphitic  carbon  (a  +  b)  and  the  combined 

carbon  (c  +  d). 

1.  Determination  of  the  Total  Carbon. — For  this,  numerous  methods 

have  been  proposed,  all  based  on  the  direct  or  indirect  combustion  of  the 

carbon.     Descriptions  will  be  given  here  of  the  Corleis  method,   of  the 

method  of  direct  combustion  in  a  current  of  oxygen  (these  two  being  most 

generally  used)  and  of  the  copper  chloride  method,  which  requires  no  special 

apparatus  and  may  be  used  in  any  laboratory. 

(a)  CORLEIS  METHOD.  This  con- 
sists in  treating  the  sample  with  a 
mixture  of  chromic  and  sulphuric 
acids  so  as  to  oxidise  all  the  carbon  to 
the  dioxide,  the  latter  being  fixed 
and  weighed. 

Reagents,  (i)  Concentrated  chro- 
mic acid  solution  :  720  grams  of 
chromic  acid,  which  need  not  be 
chemically  pure  but  must  be  free 
from  organic  matter  (the  pure  chro- 
mic acid  of  commerce),  are  dissolved 
in  700  c.c.  of  water. 

(2)  Copper  sulphate  solution  :  400 
grams  of  crystallised  copper  sulphate 
are  dissolved  to  2  litres. 

Apparatus.     The  necessary  appar- 
atus is  shown  in  Fig.  10  on  p.  165, x 
and  includes  : 
K  C1)  A  tower  A  to  purify  the   air 

\J  \   (  )  and  containing  potassium  hydroxide 

solution  at  the  bottom  and  soda 
lime  or  lump  potash  in  the  upper 
part. 

(2)  The  Corleis  flask,  modified  to 
some  extent,  consisting  of  a  700-900 
c.c.  flask  (shown  in  detail  in  Fig.  9) 
fitted  with  a  small  ground-in  con- 
denser which  descends  inside  the 
neck,  and  the  mouth  of  which  is  hol- 
lowed to  the  form  of  a  small  basin 

to  hold  sulphuric  acid  to  seal  the  ground-in  plug  ;  by  means  of  two  tubes 

a  current  of  air  may  be  passed  through  the  flask.2 

(3)  A  drying  flask  C,  charged  with  sulphuric  acid  to  about  3  mm.  below 

the  end  of  the  gas  tube. 

1  This  figure  and  many  of  the  others  shown  were  designed  by  Dr.  B.  Gasparinetti. 

2  To  prevent  breaking  of  the  flask  during  heating  it  is  well  to  wrap  the  bottom  in 
asbestos.     A  disc  of  asbestos  board  about  0-5  mm.  in  thickness  is  prepared  and  a  num- 
ber of  Jradial  slits  made  almost  to  the  centre  ;    the  disc  is  then  moistened  and  stuck 
to  the  bottom  of  the  flask.     After  drying  in  the  oven  the  asbestos  remains  perfectly 
adherent  to  the  vessel. 


IRON 


165 


(4)  A  small  glass  or  glazed  porcelain  combustion  tube  D,  filled  with 
copper  oxide  and  heated  by  two  or  three  bunsen  fan  flames,  with  the  object 
of  transforming  into  carbon  dioxide  the  small  amounts  of  carbon  monoxide 
or  hydrocarbons  which  may  be  formed  in  the  reaction. 

(5)  A  U-tube  (E)  with  ground  stoppers  and  filled  with  phosphoric  anhy- 
dride to  retain  the  moisture  in  the  gas.1 

(6)  Two  U-tubes  (F,  F),  with  ground  stoppers,  for  absorbing  the  carbon 
dioxide  ;    the  left  branch  and  half  of  the  right  are  charged  with  granular 
soda  lime  (granules  1-1-5  mm.)  covered  with  loose  glass  wool  plugs,  the 
rest  of  the  right  limb  being  filled  with  phosphoric  anhydride  also  capped 
with  a  glass  wool  plug.     One  of  these  tubes  is  usually  sufficient  to  fix  all 
the  carbon  dioxide  evolved,  and  may  be  used  for  several  determinations, 
the  other  serving  as  control.2 

(7)  A  U-tube  (G)  containing  phosphoric  anhydride  and  a  wash-bottle 
(H)  with  cone,  caustic  soda  solution  to  protect  the  absorption  tubes  from 
atmospheric  moisture  and  carbon  dioxide. 

(8)  An  aspirator  (/)  to  regulate  the  gas  current. 


FIG.  10 

Procedure.  When  the  apparatus  has  been  fitted  together  as  shown 
and  the  joints  made  air-tight,  35  c.c.  of  the  chromic  acid  solution,  150  c.c. 
of  the  copper  sulphate  solution  and  200  c.c.  of  cone,  sulphuric  acid  (D  1-84) 
are  introduced  into  the  flask  by  raising  the  ground  glass  plug  of  the  funnel 
i  ;  to  destroy  any  organic  matter  present,  the  mixture  is  boiled  for  about 
half  an  hour,  a  gentle  current  of  air  being  drawn  through  the  apparatus 
and  the  glass  or  porcelain  tube  heated.  During  this  preliminary  operation 
it  is  useless  to  insert  the  series  of  U-tubes. 

Meanwhile  the  soda  lime  tubes  are  weighed  and  also  the  sample,  which 
should  be  in  powder  or  fine  filings.3 

1  The  phosphoric  anhydride  may  be  replaced  by  calcium  chloride,  provided  that 
this  has  been  recently  saturated  with  carbon  dioxide  to  neutralise  alkalinity  due  to  the 
presence  of  lime. 

2  These  two  tubes  may  be  replaced  by  Geissler  bulbs  filled  with  30%  caustic  potash 
solution. 

3  The  sample  may  be  weighed  either  in  a  small  glass  tube  with  a  foot  and  poured 
into  the  flask  through  a  funnel  (Fig.  9,  b)  with  a  long,  wide  stern,  or  in  a  small  platinum 
bucket  which  is  suspended  in  the  liquid  in  the  flask  by  a  platinum  wire  attached  to  a 
suitable  hook  fused  on  to  the  bottom  of  the  condenser  (Fig.  9,  a),  or  in  a  small  thin-walled 
glass  tube  which  is  introduced  directly  into  the  flask. 


166  IRON 

With  pig  iron  containing  3  -4%  of  carbon,  I  gram  is  taken  ;  with  steel 
containing  more  than  0-3%,  3  grams,  and  with  soft  iron  containing  less 
than  0-3%,  5  grams. 

When  the  liquid  in  the  flask  is  quite  cold  the  absorption  bulbs  are  fitted, 
a  little  sulphuric  acid  is  placed  in  the  funnel  i,  the  condenser  is  raised  and 
the  weighed  metal  introduced  into  the  flask,  the  condenser  being  then 
rapidly  replaced  and  a  little  sulphuric  acid  poured  into  the  annular  cavity 
to  ensure  perfect  fitting. 

The  burners  under  the  combustion  tube  are  then  lighted  and  a  moderate 
current  of  air  (2-3  bubbles  per  second)  passed  through  the  apparatus,  while 
the  flask  is  heated  carefully  so  as  to  bring  the  liquid  to  boiling  in  10-15 
minutes.  Boiling  should  be  continued  for  about  3  hours,  the  flow  of  gas 
being  kept  regular  and  the  flame  being  lowered  or  removed  immediately 
if  pressure  develops  in  the  flask  and  tends  to  drive  the  liquid  along  the 
tube  used  for  the  introduction  of  the  acid. 

Towards  the  end  the  air-current  is  accelerated  a  little  to  displace  all 
the  carbon  dioxide  from  the  apparatus,  the  absorption  apparatus  being 
afterwards  closed,  the  flames  extinguished  and  the  weighings  made.  The 
total  carbon  in  the  sample  is  obtained  by  multiplying  the  carbonic  anhydride 
found  by  0-27273. 

To  ascertain  if  the  sample  has  been  acted  on  completely,  the  cold  mixture 
of  sulphuric  and  chromic  acids  is  diluted  with  a  large  amount  of  water  in 
a  large  beaker  and,  after  a  short  time,  the  deposit  collecting  at  the  bottom 
of  the  beaker  is  tested  for  iron  particles  by  means  of  a  magnet  brought  near 
to  the  outside. 

The  Corleis  method  is  usually  adopted  for  the  analysis  of  iron,  cast-iron 
and  steel,  but  is  unsuitable  with  products  difficult  of  attack  by  sulphuric- 
chromic  acid  mixture,  such  as  ferro-silicon,  ferro-chromium,  ferro-tungsten, 
etc.  For  the  latter,  the  direct  combustion  method  should  be  used  (see 
later). 

Corleis  observed  that,  in  the  determination  of  the  carbon  in  steels  under 
the  above  conditions,  only  2%  of  the  total  carbon  is  liberated  as  hydro- 
carbons, so  that  the  apparatus  may  be  simplified  by  the  suppression  of 
the  combustion  tube,  the  result  then  obtained  being  increased  by  2%. 

(&)  DIRECT  COMBUSTION  IN  A  CURRENT  OF  OXYGEN.  This  method  con- 
sists in  heating  the  sample  at  1050-1150°  in  a  current  of  oxygen  and  ab- 
sorbing the  carbon  dioxide  thus  formed  in  the  usual  way. 

Apparatus  :    (i)  Gasometer  containing  oxygen. 

(2)  Wash   bottles   containing   sodium   hydroxide   solution    and    cone, 
sulphuric  acid  respectively,  and  a  small  U-tube  with  calcium  chloride. 

(3)  A  quartz  or  externally  glazed  porcelain  combustion  tube   (50-60 
cm.  long,  1-5  cm.  bore),  closed  by  rubber  stoppers  protected  from  the  heat 
by  asbestos  board  and  containing,  at  the  end  near  the  absorption  apparatus, 
a  short  layer  of  cupric  oxide  to  oxidise  any  carbon  monoxide  which  may 
be  formed. 

(4)  An  electric  resistance  furnace  for  heating  the  tube,  with  rheostat 
and  amperemeter  (see  Fig.  n). 

(5)  A  Le  Chatelier  thermo-electric  couple  of  platinum  and  platinum- 


IRON 


167 


rhodium  wires  with  corresponding  galvanometer-pyrometer  (Fig.  n,  P,  G). 

(6)  Two  U-tubes,  one  rilled  with  pumice  and  chromic  acid  and  the  other 
with  calcium  chloride  and  phosphoric  anhydride. 

(7)  The  usual  absorption  apparatus  for  the  carbon  dioxide  (see  preced- 
ing method),  followed  by  a  sulphuric  acid  wash-bottle. 

Procedure.  When  the 
apparatus  is  arranged,  a 
moderate  current  of  oxygen 
is  passed  for  about  10 
minutes  and  then,  complete 
elimination  of  the  air  being 
ensured,  without  interrupt- 
ing the  flow  of  gas  the  ^ 
absorption  apparatus  is  de- 
tached and  weighed  when 
it  has  reached  the  tempera- 
ture of  the  surrounding  air. 

Meanwhile  the  furnace  is 
heated  and  the  sample 
weighed  in  an  unglazed  por- 
celain boat  (10-12  cm.  long, 
1-4  cm.  wide).  Of  malleable 
iron  or  ordinary  cast-iron,  i 
gram  is  taken,  or  of  iron 
alloys  rich  in  carbon,  such 
as  ferro-manganese,  ferro- 

chromium,  etc.,  0-5  gram.     The  sample  should  not  be   too  finely   pow- 
dered in  order  that  too  violent  combustion  may  be  avoided. 

When  the  furnace  reaches  a  temperature  of  about  900°,  the  stream  of 
oxygen,  is  interrupted  and  the  boat  pushed  exactly  into  the  middle  of  the 
tube  by  means  of  a  copper  wire  or  a  quartz  rod  fitted  with  a  hook,  the  tube 
being  then  quickly  closed  and  the  absorption  apparatus  attached. 

A  fairly  rapid  current  of  oxygen  is  then  passed  and  the  temperature 
of  the  furnace  raised  to  between  1050°  and  1150°  in  15-20  minutes.  The 
latter  temperature  should  not  be  exceeded,  since  otherwise  the  furnace 
may  be  damaged  and  the  sample  may  begin  to  fuse  and  enclose  a  little 
carbon,  which  may  thus  escape  complete  combustion.  The  temperature 
is  kept  at  1050-1150°  for  15-20  minutes,  the  heating  being  then  interrupted 
and  the  velocity  of  the  oxygen  increased  until  about  700°  is  reached,  when 
the  absorption  apparatus  is  detached  and,  15-20  minutes  later,  weighed. 
The  weight  of  the  carbon  dioxide,  multiplied  by  0-27273,  gives  the  carbon 
in  the  sample  taken.  After  removal  of  the  boat  the  apparatus  is  ready  for 
the  next  determination. 

In  determining  carbon  in  certain  ferro-metallic  alloys,  such  as  ferro-silicon, 
ferro-chromium  and  ferro-manganese,  it  is  necessary  to  add  a  catalyst  to  ensure 
the  complete  oxidation  of  the  carbon.  According  to  Ledebur,  the  best  results 
are  obtained  by  cobalt  oxide,  which  should  be  calcined  for  half  an  hour  in  an 
electric  furnace  at  about  1000°  before  use.  One  gram  of  the  oxide  is  mixed  in 


FIG.  1 1 


168  IRON 

an  agate  mortar  with  0-5  gram  of  ferro-chromium  or  ferro-manganese,  or  1-2 
grams  of  the  oxide  with  i  gram  of  ferro-silicon,  the  mixture  being  introduced 
quantitatively  into  the  boat  and  the  combustion  carried  out  for  1^-2  hours  at 
1050°. 

With  readily  fusible  ferro-metallic  alloys,  such  as  ferro- vanadium  and  ferro- 
molybdenum,  it  is  advisable  to  mix  with  a  little  refractory  clay. 

The  above  method  of  estimating  the  total  carbon,  which  is  coming  more  and 
more  into  general  use,  combines  exactness  with  great  rapidity  (for  ordinary  pro- 
ducts, 30-40  minutes  suffice)  and  has  the  great  advantage  over  the  Corleis  method 
that  it  is  applicable  to  any  ferrous  product. 

(c)  COPPER  CHLORIDE  METHOD.  This  method  consists  in  attacking 
the  iron  with  a  reagent,  such  as  copper-potassium  chloride,  which  leaves 
the  carbon  unchanged,  and  in  determining  the  carbon  separated  by  com- 
bustion. It  is  less  exact  but  simpler  than  the  two  preceding  methods  and 
may  always  be  used  with  advantage  for  products  rich  in  carbon. 

Such  quantity  of  the  finely  powdered  sample  is  taken  as  will  liberate 
about  0-015-0-02  gram  of  carbon  :  3  grams  of  steel  containing  about  0-5% 
of  carbon,  i  gram  of  cast  iron  with  not  much  more  than  2%  of  carbon,  and 
0-5  gram  of  products  still  richer  in  carbon. 

An  aqueous  30%  solution  of  copper-potassium  chloride  is  prepared  as 
free  as  possible  from  organic  matter,  50  c.c.  of  this  solution  being  used  per 
gram  of  metal  to  be  attacked. 

This  volume  of  the  solution  is  placed  in  a  250  c.c.  conical  flask  and 
acidified  with  a  little  hydrochloric  acid  to  prevent  the  dissolution  of  small 
quantities  of  carbonaceous  matter,  the  weighed  sample  being  then  added  and 
the  flask  shaken.  The  iron  passes  immediately  into  solution  liberating 
copper,  which,  however,  dissolves  completely  in  the  excess  of  the  reagent 
on  gentle  heating  and  shaking,  leaving  a  black  residue  containing  the  whole 
of  the  carbon.  The  action  is  usually  complete  in  about  half  an  hour. 

Any  basic  iron  salt  formed  is  then  dissolved  by  addition  of  a  few  drops 
of  hydrochloric  acid  and  the  liquid  filtered  through  a  Gooch  crucible  con- 
taining ignited  asbestos.  If  all  the  carbon  is  retained  by  the  filter,  dilution 
of  a  few  drops  of  the  brown  filtrate  with  water  acidified  with  hydrochloric 
acid  yields  a  clear,  greenish  solution.  The  flask  and  residue  are  washed 
first  with  dilute  copper-potassium  chloride  solution  acidified  with  hydro- 
chloric acid  and  then  with  distilled  water  until  the  wash  water  no  longer 
contains  chloride,  the  crucible  being  then  dried  at  a  low  temperature. 

The  asbestos  with  the  carbon  are  then  burnt  in  a  platinum  boat  in  a 
combustion  tube  through  which  oxygen  is  passed,  the  procedure  being  that 
followed  in  ordinary  elementary  analysis  of  organic  compounds.  Between 
the  combustion  tube  and  the  absorption  bulbs  for  the  carbon  dioxide  (Geissler 
bulbs),  two  U-tubes  are  inserted,  one  with  pumice  soaked  in  sulphuric  acid 
saturated  with  chromic  acid  to  oxidise  and  retain  any  sulphur  dioxide 
formed  by  oxidation  of  sulphur  or  sulphides,  and  the  other  copper  sulphate 
dehydrated  at  200°  to  catch  moisture  and  any  traces  of  hydrochloric  acid. 
CO2  X  0-27273  =  carbon. 

For  the  combustion  of  the  carbonaceous  residue  separated,  the  above  method 
may  be  replaced  by  treatment  with  chromic  and  sulphuric  acids  in  the  Corleis 
apparatus  (see  p.  164).  Certain  products,  such  as  ferro-silicon,  ferro-chromium, 


IRON  169 

ferro-tungsten,  etc.,  are  not  completely  attacked  by  copper-potassium  chloride, 
and  cannot,  therefore,  be  analysed  in  this  way  (see  p.  168). 

2.  Determination  of  the  Graphitic  Carbon  (graphitic  carbon  and 
annealing  carbon). — These  are  not  altered  by  hot  dilute  nitric  acid,  whilst 
the  combined  carbon  (hardening  carbon  and  carbide  carbon)  are  converted 
into  volatile  or  soluble  products.  On  this  difference  is  based  the  method 
of  separation  of  the  two  types  of  carbon. 

As  a  rule,  i  gram  of  grey  cast-iron  or  2-3  grams  of  white  cast-iron  or 
5-10  grams  of  steel,  are  treated  in  a  tall,  narrow  beaker  covered  with  a 
watch  glass  with  nitric  acid  of  D  1-2  (about  25  c.c.  per  gram  of  metal),  the 
beaker  being  cooled  at  first  to  prevent  an  excessively  violent  reaction. 
When  the  reaction  begins  to  slacken,  the  beaker  is  heated  on  a  sand-bath 
to  complete  the  action  and,  if  much  silicon  is  present,  when  the  metal 
is  entirely  attacked  0-5-1  c.c.  of  pure  hydrofluoric  acid  is  added  from  a 
platinum  crucible  without  touching  the  sides  of  the  beaker. 

The  liquid  is  gently  boiled  for  i-i|-  hour  and  is  then  diluted  with  water, 
the  insoluble  matter  being  allowed  to  settle  and  collected  on  a  Gooch  crucible 
and  washed  with  hot  water  until  free  from  acid. 

After  being  dried  at  not  too  high  a  temperature,  the  asbestos  and  graphitic 
residue  are  oxidised  either  in  the  Corleis  apparatus  with  chromic  and  sul- 
phuric acids  (see  p.  164)  or  in  an  open  tube  in  a  current  of  oxygen  (see  p.  167). 

According  to  Ledebur,  the  graphitic  carbon  separated  may  be  collected  and 
weighed  directly  on  a  filter  dried  at  100°  and  tared.  To  ensure  complete  removal 
of  extraneous  substances,  the  residue  should  be  washed  twice  with  hot  water, 
twice  with  hot  5%  caustic  potash  solution,  twice  with  hot  water,  twice  with  hot, 
dilute  hydrochloric  acid  (i  13),  and  finally  three  times  with  hot  water.  In  this 
case  the  addition  of  hydrofluoric  acid  to  eliminate  every  trace  of  silicon  is,  of 
course,  indispensable. 

3.  Determination  of  the  Combined  Carbon  (carbide  carbon  and 
hardening  carbon). — The  combined  carbon  in  cast-iron  may  be  calculated 
as  the  difference  between  the  total  carbon  and  the  graphitic  carbon  deter- 
mined by  the  methods  already  given. 

In  malleable  iron  and  especially  in  steel,  which  do  not  contain  graphitic 
carbon,  the  determination  of  the  combined  carbon  (in  this  case,  the  total) 
may  be  carried  out  by  the  rapid  colorimetric  method. 

COLORIMETRIC    DETERMINATION    OF    THE    COMBINED    CARBON     (Eggeitz 

method).  This  is  based  on  the  fact  that  hot  nitric  acid  leaves  the  graphitic 
carbon  unaltered,  while  the  combined  carbon  is  partly  liberated  as  gas 
(hardening  carbon)  and  partly  dissolved  in  the  acid  (carbide  carbon),  which 
is  coloured  a  more  or  less  intense  brownish-red  in  dependence  on  the  quantity 
of  carbon. 

In  general,  the  proportions  of  carbide  carbon  and  hardening  carbon  in 
untempered  steels  l  are  in  almost  constant  ratio,  so  that,  if  parallel  tests 
are  made  on  the  sample  under  examination  and  on  a  steel  with  a  known 
content  of  carbon,  the  solutions  obtained  will  have  colour  intensities  pro- 
portional, not  only  to  the  content  of  carbide  carbon  but  to  the  content  of 
total  combined  carbon. 

1  This  method  is  consequently  inapplicable  to  tempered  steels. 


170 


IRON 


u 


Procedure.  Of  the  finely  powdered  steel  and  of  a  typical  steel,  o-i  gram 
is  introduced  into  each  of  two  thick-walled  test-tubes  (123  mm.  high  and 
15  mm.  in  diam.).  Into  each  tube  5  c.c.  of  nitric  acid  (D  1-18-1-2)  free 
from  hydrochloric  acid  are  poured,  the  tube  being  covered  with  a  funnel 
and  immersed  in  a  bath  of  cold  water  to  allay  the  vigour  of  the  reaction. 
After  a  short  time  the  tubes  are  transferred  to  a  vessel  of  water  and  heated 
at  80-100°  x  for  1—2  hours,  care  being  taken  that  the  level  of  liquid  in  the 
bath  is  not  more  than  about  I  cm.  higher  than  that  in  the  tubes. 

After  1-2  hours'  heating,  when  the  action  is  at  an  end,  the 
Cp  tubes  are  cooled  in  cold  water  and  the  solutions  poured  into 
white  glass  tubes  of  the  same  bore  and  thickness,  holding  30 
cm.  and  divided  into  tenths  of  i  c.c.  (Eggertz  tubes,  see  Fig. 
12),  filtering  if  necessary  (that  is,  if  much  silica  remains) 
through  a  small  asbestos  filter  away  from  direct  light 

To  carry  out  the  colorimetric  comparison  the  volume  of 
each  solution  is  made  up  to  8  c.c.,  in  order  that  the  colour  may 
not  be  influenced  by  that  of  the  dissolved  iron  or  impurities 
and  the  colours  viewed  by  transmitted  and  reflected  light. 
The  darker  one  is  then  carefully  diluted  with  water  until  the 
intensities  correspond  ;  the  tubes  should  be  interchanged  and 
the  comparison  repeated. 

The  comparison  is  facilitated  by  the  use  of  a  box  with 
opaque,  black,  lateral  walls,  the  back  one  sliding  up  to  admit 
of  examination  by  transmitted  light.  The  combined  carbon  is 
deduced  from  the  proportion, 

V  :  v  =  C  :  x, 


FIG.  12 


where  V  and  v  are  the  respective  volumes  of  solution  from  the 
control  steel  and  the  steel  under  examination  and  C  and  x  the 
corresponding  contents  of  combined  carbon. 


With  practice  the  colorimetric  method  gives  sufficiently  exact  results  and  is 
rapid  and  permits  of  several  simultaneous  determinations.  It  is  naturally  of 
advantage  to  compare  steels  of  the  same  kind,  e.g.,  a  Martin  steel  with  another 
Martin  steel  and  a  Bessemer  steel  with  a  Bessemer  steel,  and  the  control  steel — the 
carbon-content  of  which  should  be  determined  very  accurately  by  combustion- 
should  have  about  the  same  content  of  carbon  as,  or  better  a  rather  greater 
content  than,  the  steel  to  be  examined.  In  general  it  is  sufficient  to  have  a 
series  of  control  steels  containing  approximately  :  0-06,  0-12,  0-15,  0-20,  0-30, 
0-50,  0-80  and  1-20%  of  carbon.  If  the  steel  has  a  carbon-content  greater  than 
0-8%,  the  calculation  may  be  simplified  by  diluting  the  solution  of  the  control 
steel  to  such  a  volume  that  the  number  expressing  the  c.c.  corresponds  with  the 
carbon-content  of  the  steel  (the  solution  of  a  control  steel  containing,  say,  0-9% 
of  carbon  would  be  diluted  to  9  c.c.).  When  the  solution  from  the  steel  to  be 
tested  has  the  same  colour  as  that  from  the  control  steel,  its  volume  divided  by 
10  gives  at  once  the  percentage  of  carbon. 

The  colorimetric  method  cannot  be  used  for  steels  containing  metals  capable 
of  modifying  appreciably  the  coloration  of  the  nitric  acid  solution,  such  as 
chromium,  copper,  nickel,  etc. 

1  The  temperature  is  easily  maintained  at  80-100°  by  placing  the  bath  containing 
the  tubes  on  a  boiling  water- bath. 


IRON  171 

2.    Determination  of  the  Silicon 

When  wrought-iron,  cast-iron  and  steels  are  dissolved  in  mineral  acids,  the 
silicon  present  separates,  after  evaporation,  as  silica  which  may  be  collected 
and  weighed.  In  practice,  the  metal  is  treated  sometimes  with  hydrochloric 
and  sometimes  with  nitric  acid  (in  some  cases  sulphuric  and  nitric  acids 
together),  according  to  the  operations  to  be  carried  out  subsequently  on 
the  liquid.  Thus,  if  only  the  silicon  is  to  be  determined  or  if  the  liquid 
is  to  be  used  for  estimations  not  affected  by  the  presence  of  hydrochloric 
acid,  the  latter  is  preferred  owing  to  its  more  rapid  action.  In  some  cases, 
however,  the  next  estimation  to  be  made  with  the  liquid — e.g.,  that  of 
phosphorus — renders  necessary  the  use  of  nitric  acid.  Both  methods  of 
acting  on  the  metal  are  in  common  use  and  will  be  described.1 

1.  Attack  of  the  Metal  with  Hydrochloric  Acid.— In  a  porcelain 
dish  covered  with  a  clock-glass  2-4  grams  of  the  sample  2  are  heated  with 
hydrochloric  acid  of  D  1-12  (about  10  c.c.  per  gram  of  metal)  on  the  water- 
bath  until  the  iron  is  completely  dissolved.  The  clock-glass  is  then  removed 
and  washed  into  the  basin  and  the  liquid  evaporated  to  dryness  on  the 
water-bath,  care  being  taken  to  mix  with  a  platinum  spatula  the  mass  of 
ferric  chloride  separating ;  the  residue  is  then  heated  for  an  hour  in  an 
oven  at  135°. 

When  cold,  the  dish  is  again  covered  with  a  clock-glass  and  the  residue 
moistened  with  10  c.c.  of  hydrochloric  acid  (D  1-12),  heated  for  some  time 
on  the  steam-bath,  diluted  with  100-150  c.c.  of  hot  water,  mixed  and,  after 
cooling,  filtered,  the  residue  being  washed  with  cold  water  acidified  with 
hydrochloric  acid  until  the  wash  water  is  free  from  iron.  At  this  point  a 
few  drops  of  hydrochloric  acid  (D  1-12)  are  allowed  to  flow  down  the  edge 
of  the  filter,  which  is  again  washed  with  cold  distilled  water. 

The  moist  filter  is  placed  point  upwards  in  a  tared  platinum  crucible 
and  carefully  burnt,  the  crucible  being  ignited  for  4-5  minutes  in  the  blow- 
pipe flame  and,  when  cold,  weighed. 

The  silica  thus  separated  may  contain  various  impurities,  such  as  graphi- 
tic carbon,  traces  of  ferric  oxide,  tungsten  oxide,  titanic  acid,  etc. 

To  determine  the  true  silica  content,  the  weighed  residue  is  treated  in 
the  crucible  with  1-2  c.c.  of  water,  1-2  drops  of  cone,  sulphuric  acid  and 
5-6  c.c.  of  hydrofluoric  acid  (puriss.).  Evaporation  is  then  carried  as  far 
as  possible  on  the  steam-bath  and  the  slight  excess  of  sulphuric  acid  expelled 
by  heating  the  inclined  crucible  over  a  small  flame.  When  evolution  of 
sulphuric  acid  vapour  ceases,  the  crucible  is  heated  to  redness  and  weighed 
when  cold.  The  loss  in  weight  gives  the  silica  and  this,  multiplied  by 
0-4693,  the  silicon. 

It  sometimes  happens,  especially  with  cast-iron  rich  in  graphite,  that 
the  silica  separated  is  grey.  In  this  case,  the  treatment  with  hydrofluoric 
acid  is  omitted  and  the  contents  of  the  crucible  heated  to  gentle  fusion 
with  a  little  sodium  carbonate  and  potassium  nitrate.  When  cold,  the  mass 

1  For  the  determination  of  silicon  in  products  insoluble  in  acid,  see   Ferro-silicon. 
"  With  samples  containing  little  silicon,  such  as  ordinary  carbon  steels,  5-10  grams 
are  taken. 


172  IRON 

is  dissolved  in  water  and  the  solution  transferred  to  a  porcelain  dish  and 
acidified  with  hydrochloric  acid.  After  evaporation  to  dryness  on  a  steam- 
bath,  the  residue  is  moistened  with  hydrochloric  acid  and  again  evaporated, 
heated  in  an  oven  at  135°,  taken  up  with  hydrochloric  acid,  diluted,  heated 
and,  after  cooling,  filtered  ;  the  silica  is  subsequently  washed,  dried,  ignited 
in  a  platinum  crucible  and  weighed. 

2.  Attack  of  the  Metal  with  Nitric  Acid. — With  grey  east-iron  or 
silicon  steel  (3  -5%  Si),  2  -4  grams,  or  with  white  cast-iron  or  ordinary  steel, 
5-10  grams,  of  the  sample  are  introduced  into  a  thin  porcelain  dish  12-15 
cm.  in  diameter.  The  dish  is  covered  with  a  clock-glass  and  dilute  nitric 
acid  (D  1-18)  gradually  added,  addition  of  fresh  acid  being  made  only  when 
the  initial  vigorous  action  begins  to  slacken.  Each  gram  of  metal  requires 
about  12  c.c.  of  acid. 

When  the  required  amount  of  acid  has  been  added,  the  dish  is  heated 
on  a  steam-bath  to  complete  the  action  *  ;  the  clock-glass  is  then  removed 
and  washed  and  the  liquid  evaporated  on  a  steam-bath,  the  dish  being 
frequently  shaken  to  break  the  skin  forming  on  the  surface,  and  towards 
the  end  of  the  operation  the  liquid  stirred  with  a  platinum  spatula  to  pre- 
vent spurting.  When  dry,  the  residue  is  heated  further  on  a  sand-bath 
or  asbestos  until  a  powdery  residue  remains  ;  the  heat  is  then  gradually 
increased  to  redness,  which  is  maintained  until  the  nitrates  are  completely 
decomposed,  i.e.,  until  evolution  of  brown  vapours  ceases. 

The  cold  residue  is  moistened  with  cone,  hydrochloric  acid  and  heated 
for  a  short  time,  a  further  addition  of  9-10  c.c.  of  cone,  hydrochloric  acid 
per  gram  of  metal  dissolved  being  made  and  the  liquid  heated  and  stirred 
until  the  ferric  oxide  is  completely  dissolved.  To  ensure  that  the  silica 
becomes  absolutely  insoluble,  the  hydrochloric  acid  solution  is  evaporated 
to  dryness  and  the  residue  heated  for  an  hour  in  an  oven  at  135°. 

The  residue  is  taken  up  again  in  cone,  hydrochloric  acid  (5-6  c.c.  of 
acid  per  gram  of  metal),  heated,  diluted  and,  when  cold,  filtered,  the  silica 
being  purified  in  the  same  way  as  when  the  metal  is  attacked  with  hydro- 
chloric acid  (see  p.  171). 

The  filtrate  may  be  used  for  the  determination  of  phosphorus  (see  p. 
173). 

3.    Determination  of  Manganese 

Manganese,  which  is  always  present  in  larger  or  smaller  amount  in  iron, 
cast-iron  or  steel,  may  be  estimated  gravimetrically,  volumetrically  or 
colorimetrically.  The  volumetric  method  will  be  described  later  (see  Ferro- 
manganese)  and  here  will  be  given  only  the  colorimetric  method,  which, 
owing  to  its  rapidity,  is  the  most  commonly  used  for  determining  the  small 
proportions  of  manganese  contained  in  iron  and  in  ordinary  steels. 

Colorimetric  Determination  of  Manganese  (according  to  Ledebur). 
—This  method  consists  in  acting  on  the  sample  with  nitric  acid,  oxidising 

1  The  more  or  less  intensely  brown  liquid  should,  however,  be  clear  ;  if  it  appears 
turbid,  a  little  more  acid  should  be  added. 


IRON  173 

the   manganese   to   permanganic   acid  and   comparing   the   colour  of  the 
solution  with  that  of  a  permanganate  solution  of  known  titre.1 

Preparation  of  the  control  solution  2  :  0-072  gram  of  chemically  pure 
potassium  permanganate  is  dissolved  in  water  and  the  volume  made  up 
exactly  to  500  c.c.  ;  i  c.c.  of  this  solution  corresponds  with  0-05  m.  grm . 
of  manganese. 

Procedure.  0-2  gram  of  the  metal  is  dissolved  in  the  hot  in  15^-20  c.c. 
of  nitric  acid  (D  1-2)  in  a  100  c.c.  measuring  flask,  the  liquid  being  after- 
wards heated  to  boiling  to  expel  nitrous  fumes,  cooled,  made  up  to  volume 
and  mixed. 

Four  portions,  each  of  10  c.c.,  are  pipetted  into  four  beakers  of  about 
75  c.c.  capacity,  2  c.c.  of  nitric  acid  (D  1-2)  being  added  to  each  beaker. 
The  first  portion  is  heated  over  a  small  flame  to  boiling,  the  beaker  being 
covered  with  a  clock-glass  meanwhile.  The  cover  is  then  quickly  removed, 
about  0-5  gram  of  lead  peroxide  free  from  manganese  added  to  the  boiling 
liquid  and  gentle  boiling  maintained  for  two  minutes  longer. 

When  cold,  the  liquid  is  filtered  by  decantation — care  being  taken  that 
no  lead  peroxide  passes — through  a  small  asbestos  (this  being  ignited,  and 
washed  with  permanganate  solution  and  then  with  water)  filter,  the  filtrate 
being  collected  in  an  Eggertz  tube  (see  Fig.  12,  p.  170)  and  the  residual 
lead  peroxide  and  the  filter  washed  with  about  5  c.c.  of  water  until  the 
wash  water  passes  through  colourless.  The  solution  in  the  Eggertz  tube, 
when  shaken,  is  ready  for  the  colorimetric  observation. 

The  other  three  portions  are  treated  in  the  same  way,  the  filtrations 
being  effected  with  the  same  filter  and  the  liquids  collected  in  Eggertz  tubes 
to  serve  for  confirmatory  purposes. 

The  colorimetric  comparison  is  made  by  pipetting  into  another  Eggertz 
tube  1-4  c.c.  of  the  control  permanganate  solution  according  to  the  colour 
intensity  of  the  other  tubes,  and  diluting  carefully  with  water  until  an  exact 
match  is. obtained. 

If  the  volume  of  the  solution  from  the  sample  of  steel  is  v  and  i  c.c.  of 
the  control  solution  has  to  be  diluted  to  V  c.c.  to  give  the  same  depth  of 
colour,  the  percentage  of  manganese  in  the  sample  will  be 

v  X  0-05 
—  -X5- 

This  rapid  and  fairly  accurate  method  cannot  be  applied  to  materials  con- 
taining more  than  1-1-5%  of  manganese. 

4.    Determination  of  the  Phosphorus 

Many  methods  are  in  use  for  the  determination  of  phosphorus  in  ferrous 
products,  those  most  generally  employed  being  based  on  the  conversion 
of  the  phosphorus  into  phosphoric  acid  and  precipitation  of  the  latter  with 
ammonium  molybdate.  The  ammonium  phosphomolybdate  separated 
may  be  determined  gravimetrically,  volumetrically,  densimetrically,  etc. 
Descriptions  will  be  given  here  of  Finkener's  gravimetric  method,  which 

1  Some  prefer  to  make  the  comparison  with  a  steel  of  known  manganese  content. 

2  This  solution,  stored  in  the  dark,  keeps  for  about  three  weeks. 


174  IRON 

is  considered  the  most  exact,  and  the  rapid  method  of  weighing  the  ammo- 
nium phosphomolybdate  directly,  with  references  to  the  modifications 
necessitated  in  both  methods  by  the  presence  of  arsenic,  vanadium  and 
tungsten.1 

1.  Gravimetric  Determination  of  Phosphorus  in  absence  of 
Arsenic,  Vanadium  and  Tungsten. 

(a)  FINKENER'S  METHOD.  Reagents  :  (i)  Ammonium  molybdate  solu- 
tion, prepared  by  dissolving  80  grams  of  powdered  ammonium  molybdate 
in  a  mixture  of  640  c.c.  of  water  and  160  c.c.  of  20%  ammonia  (D  =  0-925) 
and  pouring  this  solution  into  a  cold  mixture  of  960  c.c.  of  30%  nitric  acid 
(D  =  1-18)  and  240  c.c.  of  water.  This  reagent  should  be  left  at  rest  for 
some  days  in  the  dark. 

(2)  Washing  liquid,  prepared  by  dissolving  150  grams  of  ammonium 
nitrate  in  water,  adding  10  c.c.  of  cone,  nitric  acid  and  diluting  to  i  litre. 

Procedure.  5  grams  of  slightly  phosphoric  iron  or  steel,  or  1-2  grams 
of  cast-iron,  or  0-5-1  gram  of  material  very  rich  in  phosphorus,  are  treated 
in  a  porcelain  dish  with  nitric  acid  of  D  =  1-2  (about  12  c.c.  per  gram  of 
metal),  the  liquid  being  evaporated  to  dryness  and  the  residue  ignited  and 
treated  with  hydrochloric  acid  and  the  silica  removed  and  determine  if 
required  as  in  the  estimation  of  silicon  by  the  nitric  acid  method  (see  p. 
172). 

The  hydrochloric  acid  solution  is  evaporated  to  a  syrup  in  a  250  c.c. 
beaker,  this  allowed  to  cool  (no  basic  iron  salt  should  separate  on  cooling) 
and  50-100  c.c.  of  the  molybdic  reagent  (according  to  the  amount  of  phos- 
phorus present)  stirred  in  by  means  of  a  rod  to  facilitate  the  separation 
of  the  precipitate.  After  a  stand  of  about  half  an  hour  in  the  cold,  chemi- 
cally pure  solid  ammonium  nitrate  is  added  to  the  extent  of  about  25%  of 
the  liquid,  the  salt  being  dissolved  by  stirring. 

After  18-24  hours  at  the  ordinary  temperature,  the  clear  supernatant 
liquid  is  filtered  by  decantation,  the  filtrate  being  collected  in  a  300  c.c. 
conical  flask,  the  beaker  and  precipitate  washed  with  the  washing 
liquid  mentioned  above  until  the  latter  no  longer  gives  the  reaction  for  iron, 
and  the  precipitate  then  transferred  to  the  filter.2 

A  few  c.c.  of  hot  dilute  ammonia  solution  are  then  poured  into  the 
beaker  to  dissolve  the  small  quantity  of  adherent  precipitate  and,  a  porcelain 
crucible  of  30-45  c.c.  capacity- — tared  with  the  lid— having  been  placed 
under  the  funnel,  the  ammoniacal  solution  is  poured  carefully  on  to  the 
filter,  the  precipitate  rapidly  dissolving.  The  beaker  and  filter  are  washed 
with  faintly  ammoniacal  water  and  the  solution  evaporated  on  a  water- 
bath  to  expel  the  ammonia,  the  volume  being  reduced  to  8  -10  c.c.  ;  4-5 
drops  of  cone,  nitric  acid  are  then  added  to  bring  about  the  re-formation 
of  ammonium  phosphomolybdate  and  the  solution  evaporated  to  dryness. 

The  crucible  is  next  heated  in  an  ordinary  air-oven  or,  better,  a  Finkener 

1  For  the  determination  of  phosphorus  in  products  unattacked  by  acids,  see  Ferro- 
silicon. 

2  When  the  precipitate  is  transferred  to  the  filter,  it  is  well  to  replace  the  300  c.c. 
flask  by  a  smaller  one  in  order  that  less  liquid  will  require  filtering  should  the  filtrate 
pass  through  turbid. 


IRON  175 

oven,  to  eliminate  the  ammonium  nitrate,  the  temperature  being  raised 
gradually  to  160-180°  ;  excessive  heating  must,  however,  be  avoided  as 
it  entails  the  danger  of  reducing  the  molybdic  acid.  If  a  dry,  cold  watch- 
glass  placed  on  the  crucible  does  not  become  dimmed  in  about  half  a  minute, 
the  expulsion  of  the  ammonium  salts  is  complete  and  the  hot  crucible  is 
allowed  to  cool  in  a  desiccator  and  weighed  as  rapidly  as  possible  to  prevent 
absorption  of  moisture.  (Ammonium  phosphomolybdate)  X  0-0164  = 
phosphorus. 

As  already  mentioned,  phosphorus  may  be  determined  directly  in  the  liquid 
from  which  the  silica  has  been  filtered,  in  the  case  when  the  metal  was  dissolved 
in  nitric  acid.  In  this  case  the  hydrochloric  acid  solution  freed  from  silica  is 
evaporated  to  a  syrup  in  a  250  c.c.  beaker,  allowed  to  cool  (no  basic  iron  salt 
should  separate)  and  50-100  c.c.  of  molybdate  reagent  added  according  to  the 
quantity  of  phosphorus  present,  the  remaining  procedure  being  as  above. 
When  a  large  amount  of  substance  has  been  taken  for  the  silicon  estimation, 
the  phosphorus  determination  is  made  on  an  aliquot  part  of  the  filtrate. 

Further,  if  a  very  large  amount  of  phosphomolybdate  separates,  some  prefer 
to  dissolve  it  in  ammonia  and  filter,  and  precipitate  by  means  of  magnesia  mix- 
ture. In  this  case,  the  magnesium  ammonium  phosphate  is  collected  on  a  filter 
after  6-7  hours,  and  washed  with  slightly  ammoniacal  water  until  the  washings 
pass  through  free  from  chlorine,  the  paper  precipitate  being  incinerated 
together  at  not  too  high  a  temperature  and  then  strongly  ignited  to  constant 
weight  in  a  blowpipe  flame  :  Mg2P2O7  X  0-2787  =  P. 

(b)  DIRECT  WEIGHING  OF  THE  AMMONIUM  PHOSPHOMOLYBDATE  (Rapid 
method). — 5  grams  of  iron  or  steel  of  low  phosphorus  content,  or  1-2 
grams  of  cast-iron,  or  0-5-1  gram  of  material  rich  in  phosphorus,  are  heated 
in  a  conical  flask  with  nitric  acid  of  D  =  1-2  (about  12  c.c.  of  acid  per  gram 
of  metal)  and  the  solution  treated  with  1—2  c.c.  of  hydrofluoric  acid  x  to 
eliminate  the  silica  and  then  heated  for  a  few  minutes  longer.2  To  oxidise 
the  phosphorus  completely,  5-10  c.c.  of  2%  permanganate  solution  are 
added  with  shaking  and  the  heating  continued  for  2-3  minutes,  3-4  c.c. 
of  25%  potassium  oxalate  being  then  added  and  the  liquid  heated  until 
the  separated  manganese  dioxide  completely  dissolves.  Ammonia  is  next 
added,  drop  by  drop,  to  the  clear  solution  until  the  first  flocks  of  ferric 
hydroxide  separate,  these  being  dissolved  by  a  few  drops  of  nitric  acid. 
The  liquid  is  then  transferred  to  a  beaker  and  evaporated  to  a  syrup,  allowed 
to  cool  to  50°  and  treated  with  50-100  c.c.  of  ammonium  molybdate  solution 
previously  heated  to  50°,  and,  after  some  time,  15-20  grams  of  solid  ammo- 
nium nitrate,  which  is  dissolved  by  shaking.  After  the  beaker  has  been 
left  for  about  an  hour  at  45-50°,  the  phosphomolybdate  precipitate  is 
collected  on  a  tared  Gooch  crucible  containing  asbestos  which  has  been 
previously  ignited  and  washed  with  nitric  acid  and  then  with  water.  The 
precipitate  is  washed  with  water  acidified  with  i%  of  nitric  acid  of  D  =  1-2 
until  the  liquid  passing  through  is  free  from  iron  and  is  then  heated  in  an 

1  The  hydrofluoric  acid  is  poured  in  from  a  platinum  dish  or  crucible  in  such  a  way 
that  it  does  not  come  into  contact  with  the  walls  of  the  flask. 

2  If  the  sample  contains  much  graphitic  carbon  the  solution,  after  treatment  with 
hydrofluoric  acid,  is  made  up  to  a  definite  volume  and  filtered  through  a  dry  filter,  an 
aliquot  part  being  taken,  treated  with  permanganate,  and  so  on. 


1 76  IRON 

oven  at  70-80°  to  constant  weight.1  Phosphomolybdate  x  0-0164  — 
phosphorus. 

2.  Determination  of  the  Phosphorus  in  presence  of  Arsenic. — 

If  not  more  than  0-1%  of  arsenic  is  present,  the  methods  described  above 
give  accurate  results,  but  with  larger  proportions  of  arsenic,  the  latter 
must  be  eliminated  from  the  phosphorus  precipitate.  After  the  metal 
has  been  acted  on,  the  silica  removed,  etc.,  as  before,  the  hydrochloric  acid 
solution  is  treated  in  a  roomy  dish,  gradually  and  with  stirring,  with  10-20 
c.c.  of  pure  hydrobromic  acid  2  of  D  =  1-49  (containing  about  48%  of 
hydrobromic  acid)  and  evaporated  to  dryness  on  a  water-bath.  The  arsenic 
is  thus  volatilised,  probably  as  the  tribromide,  whilst  all  the  phosphorus 
remains.  The  residue  is  taken  up  in  dilute  hydrochloric  acid,  the  solution 
evaporated  in  a  250  c.c.  beaker  to  a  syrup,  and  the  phosphoric  acid  pre- 
cipitated as  usual. 

3.  Determination   of   Phosphorus   in   presence   of   Vanadium.— 
In   presence   of   vanadium,   the   ammonium   phosphomolybdate,   which  is 
then   orange-coloured,   is   dissolved  in   dilute   ammonia   and   the   solution 
evaporated  to  20  c.c.,  a  few  drops  of  dilute  ammonia  being  added  from  time 
to  time.      The  cooled-slightly  ammoniacal  liquid  is  then  saturated  with 
ammonium  chloride  (5-6  grams  are  added),  care  being  taken    that   undis- 
solved  crystals  remain  in  the  solution.     The  vanadium  is  thus  precipitated 
as  ammonium  metavanadate  which,  after  6~io  hours,  is  filtered  and  washed 
with  ammonium  chloride  solution  (250  grams  per  litre)  until  the  washings 
no  longer  give  the  phosphate  reaction  with  molybdate,  the  phosphate  being 
then  precipitated  in  the  filtrate  by  means  of  magnesia  mixture. 

4.  Determination  of  Phosphorus  in   presence  of  Tungsten. — In 
this  case  the  phosphomolybdate  precipitate  is  dissolved  in  ammonia  and 
the  phosphate  precipitated  with  magnesia  mixture  (see  p.  175). 

5.    Determination  of  the  Sulphur 

Of  the  various  methods  proposed,  the  gravimetric  and  volumetric 
methods  will  be  given  here. 

1.  Gravimetric  Determination.- — (a)  M.  Arnold's  method3:  6 
grams  of  the  sample  are  mixed  with  i  gram  of  potassium  chlorate  and 
treated  in  a  porcelain  dish  covered  with  a  clock-glass  with  50  c.c.  of  cone, 
nitric  acid  containing  in  solution  i  c.c.  of  bromine.  When  evolution  of 
gas  ceases,  10  c.c.  of  hydrochloric  acid  are  added  and  the  liquid  evaporated 
to  dryness  on  a  sand-bath  and  the  residue  heated  in  an  oven  at  105°  for 
5-6  hours.  The  residue  is  then  taken  up  in  30  c.c.  of  hydrochloric  acid, 
the  liquid  evaporated  to  10  c.c.,  diluted  with  water  and  the  solution  poured 
into  a  60  c.c.  measuring  flask,  made  up  to  volume  and  filtered  through  a 
dry  pleated  filter. 

Of  the  filtrate,  50  c.c.  (corresponding  with  5  grams  of  the  sample)  are 

1  The  slight  reduction  of  the  phosphomolybdate  observable  round  the  walls  of  the 
crucible  has  scarcely  any  influence  on  the  accuracy  of  the  result. 

8  The  freedom  of  this  acid  from  phosphorus  must  be  ascertained  by  a  blank  test. 
3  For  acting  on  the  metal,  Campredon's  modification  is  followed. 


IRON  177 

treated  in  a  beaker  in  the  cold  with  20  c.c.  of  10%  barium  chloride  solution. 
The  volume  is  made  up  to  about  100  c.c.  with  water,  the  liquid  stirred 
and,  after  standing  for  12-24  hours,  filtered  by  decantation  and  the  pre- 
cipitate finally  transferred  to  the  filter  and  washed  alternately  with  hot 
dilute  hydrochloric  acid  (10%)  and  cold  water  until  the  washings  no  longer 
give  the  iron  reaction  with  thiocyanate.  The  barium  sulphate  thus 
obtained,  which  should  be  perfectly  white,  is  dried,  ignited  and  weighed  : 
BaSO4  x  0-1374  =  S  (in  5  grams  of  sample). 

This  method  is  moderately  delicate.  In  presence  of  large  quantities  of  iron 
the  precipitation  may  sometimes  be  incomplete  or  the  barium  sulphate  may 
contain  iron  as  an  impurity.  This  difficulty  is  obviated  by  Meinecke  1  and 
by  Carnot  and  Goutal  z  by  the  following  method  (see  b] ,  the  iron  being  removed 
by  means  of  copper-potassium  chloride,  and  the  oxidation  of  the  sulphur  being 
made  on  the  insoluble  residue,  which  contains  the  sulphur  as  sulphides  of  copper 
and  iron  and  only  very  little  of  the  latter. 

(b)  MEINECKE,  CARNOT  AND  GOUTAL'S  METHOD.  5  grams  of  the 
finely  powdered  sample  are  heated,  with  frequent  shaking,  with  about  50 
grams  of  copper-potassium  chloride  and  250  c.c.  of  water  (see  Determination 
of  carbon  by  means  of  copper  chloride)  for  about  15  minutes  on  a  water- 
bath,  10  c.c.  of  hydrochloric  acid  being  then  added  and  the  liquid  again 
heated  to  dissolve  the  separated  metallic  copper.  The  insoluble  residue 
is  then  collected  on  a  small  paper  or  asbestos  filter  and  washed  with  hot 
water.  The  filter  and  precipitate  are  then  evaporated  on  a  water-bath 
to  dryness  in  a  small  dish  with  a  little  potassium  chlorate,  5  c.c.  of  nitric 
acid  (D  1-4)  and  10  c.c.  of  hydrochloric  acid  (D  1-19).  The  residue  is  then 
taken  up  with  a  little  hydrochloric  acid,  again  heated  almost  to  dryness 
on  a  water-bath,  diluted,  and  filtered  and  washed  with  hot  water.  The 
filtrate  is  neutralised  with  ammonia,  acidified  slightly  with  hydrochloric 
acid  and  precipitated  in  the  hot  with  barium  chloride. 

This  method  is  sufficiently  exact  and  rapid. 

2.  Volumetric  Determination  of  the  Sulphur  (Rollet  &  Campredon's 
method). — When  wrought-iron,  cast-iron  or  steel  is  acted  on  by  hydrochloric 
or  sulphuric  acid,  the  sulphur  present  is  liberated  mostly  as  hydrogen  sulphide 
and  in  small  part  as  sulphur  compounds  [especially  (CH3)2S],  which  may 
be  reduced  to  hydrogen  sulphide  by  heating  in  presence  of  hydrogen  in  a 
porcelain  tube.  The  hydrogen  sulphide  is  fixed  by  zinc  acetate  and  the 
sulphide  formed  determined  iodometrically. 

Reagents :  (i)  25  grams  of  pure,  crystallised  zinc  acetate  and  I  c.c.  of 
acetic  acid  dissolved  to  i  litre. 

(2)  7-928  grams  of  resublimed  iodine  are  dissolved  with  the  help  of 
25  grams  of  potassium  iodide  and  the  volume  made  up  to  i  litre  :  3  i  c.c. 
corresponds  with  o-ooi  gram  of  sulphur.4 

1  Zeitschr.  angew.  Chem.,   1888,  p.  376.  2  Compt.  rend.,   1897. 

3  The  litre  of  the  iodine  solution  may  be  controlled  by  comparing  the  thiosulphate 
solution  with  iodine  by  the  method  used  for  determining  the  iodine  number  of  fatty 
substances  (see  chapter  on  Fatty  Materials)  and  then  titrating  the  thiosulphate  and 
iodine  solutions. 

4  The  reaction  between  zinc  sulphide  and  iodine  takes  place  thus  :    Zn  S  +  2!  = 
ZnI2  +  S,  so  that  32  parts  of  sulphur  require  257-7  parts  of  iodine  or  i  gram  of  sulphur, 

A.C.  12 


178 


IRON 


(3)  10  grams  of  pure  sodium  thiosulphate  and  2  grams  of  ammonium 
carbonate  are  dissolved  to    i    litre  ;     10  c.c.    of   the   iodine   solution    are 
decolorised  by  about  15  c.c.  of  the  thiosulphate  solution. 

(4)  Starch  paste. 

Titration  of  the  thiosulphate  solution.     The  thiosulphate  solution  is  run 
from  a  burette,  with  continual  shaking,  into  a  bottle  like  those  shown  at 
EE1  (Fig.  13)  containing  200  c.c.  of  zinc  acetate  solution  and  a  measured 
volume  (e.g.,  10  c.c.)  of  the  iodine  solution.     When  a  pale  yellow  colour 
is  reached,  the  titration  is  completed  in  presence  of  starch  paste.     If  10 
c.c.  of  the  iodine  solution  require,  say,  15  c.c.  of  the  thiosulphate,  i  c.c. 
of  the  latter  will  be  equivalent  to  o-oi  -i-  15  =  0-00066  gram  of  sulphur. 
Apparatus  :    The  apparatus  shown  in  Fig.  13  is  required,  including  : 
Two  Kipps,  one  for  carbon  dioxide  and  the  other  for  hydrogen. 


FIG.  13 

A  wash-bottle  A  containing  about  150  c.c.  of  2%  silver  nitrate  solution  ; 
both  gases  are  purified  by  passage  through  this  solution. 

Two  wash-bottles  B  and  B1  containing  about  100  c.c.  of  the  2%  silver 
nitrate  solution  and  distilled  water  respectively. 

A  flask  C  of  500  c.c.  capacity  (the  Corleis  flask  used  for  determining  the 
total  carbon  does  well)  furnished  with  a  three-holed  stopper,  traversed  by 
(i)  a  right-angled  tube  reaching  almost  to  the  bottom  of  the  vessel  and 
serving  to  conduct  the  hydrogen  and  carbon  dioxide,  (2)  the  stem  of  a 
tapped-funnel  for  introducing  the  acid  to  attack  the  metal,  and  (3)  the  end 
of  a  small  condenser  connected  with  a  porcelain  tube  glazed  internally 
which  can  be  heated  to  cherry- redness  in  a  suitable  furnace  D. 

An  absorption  flask  E  containing  200  c.c.  of  the  zinc  acetate  solution 
and  a  second  El  containing  50  c.c.  of  the  same  solution  and  serving  as  check. 

Procedure.  The  flasks  E  and  El  being  charged,  5  grams  of  the  metal  are 
placed  in  the  flask  and  the  air  in  the  apparatus  expelled  by  carbon  dioxide. 
The  porcelain  tube  is  then  gradually  heated  to  redness  and  a  mixture  of 
60  c.c.  of  dilute  hydrochloric  acid  (i  vol.  HC1  to  2  vols.  of  water)  with  30 
c.c.  of  dilute  sulphuric  acid  (i  vol.  H2S04  to  4  vols.  of  water)  run  in  by 
means  of  the  funnel.  The  acids  are  allowed  to  act  for  some  time  in  the 
cold  ;  in  the  meantime,  the  current  of  carbon  dioxide  is  replaced  by  one 

7-928  grams;     i  c.c.  of  the  solution  containing   7-928   grams   of  iodine  per  litre   will, 
therefore,  correspond  with  o-ooi  gram  of  sulphur. 


IRON  179 

of  hydrogen,1  and  after  about  5  minutes  the  flask  is  gently  heated  to  com- 
plete the  action,  which  may  occupy  15-30  minutes,  according  to  the  nature 
of  the  metal. 

The  hydrogen  in  the  apparatus  is  then  displaced  by  carbon  dioxide. 
The  bottle  E1  is  then  emptied  and  washed  into  E  and  an  exactly  measured 
volume  of  the  iodine  solution  (10,  20  or  30  c.c.  according  to  the  amount  of 
the  precipitate)  added.  After  some  time,  during  which  the  flask  is  occa- 
sionally shaken,  the  excess  of  iodine  is  titrated  with  the  thiosulphate  solution 
in  the  usual  way. 

Example  :  10  c.c.  of  iodine  solution  were  taken  and  n  c.c.  of  thiosulphate 
solution  were  required  to  decolorise  the  excess  of  iodine.  The  sulphur  has  there- 
fore absorbed  iodine  equivalent  to  15—11  =4  c.c.  of  thiosulphate,  the  amount 
of  sulphur  thus  being  0-00066  x  4,  and  the  percentage  of  sulphur  in  the  sample 
(4  X  0-00066  X  100)  -^  5  =  0-053. 

This  method  gives  excellent  results  and  is  simple  to  execute.  It  is  especially 
advantageous  when  determinations  have  to  be  made  regularly,  since,  when 
the  apparatus  is  fitted  up  and  the  solutions  ready,  a  determination  can  be  made 
in  about  30  minutes. 


6.    Determination  of  the  Arsenic 

Arsenic  may  be  determined  fairly  simply  by  distilling  as  trichloride 
and  titrating  the  distillate  with  iodine  solution. 

Reagents  :    (i)  Solution  of  iodine  in  potassium  iodide.2 

2.  Starch  paste. 

Titration  of  the  iodine  solution.  According  to  Tread  well,  the  titre  of 
the  iodine  solution  with  respect  to  arsenic  is  ascertained  by  dissolving,  in 
the  hot,  1-32  gram  of  arsenious  acid  (puriss.)  in  the  least  possible  quantity 
of  concentrated  caustic  soda  solution,  the  liquid  being  transferred  quan- 
titatively to  a  litre  flask,  and  a  drop  of  phenolphthalein  and  sufficient  dilute 
sulphuric  acid  to  decolorise  the  liquid  being  added. 

About  20  grams  of  sodium  bicarbonate  are  dissolved  in  500  c.c.  of  cold 
water  and  the  solution  filtered  and  added  to  that  of  the  arsenious  anhydride. 
If  the  liquid  is  still  red,  a  few  drops  of  dilute  sulphuric  acid  are  added  and 
the  volume  made  up  to  i  litre  :  i  c.c.  of  this  solution  contains  i  m.  grm. 
of  arsenic.  Into  50  c.c.  of  this  solution  (0-050  gram  arsenic)  mixed  with 
a  little  starch  paste,  the  iodine  solution  is  run  from  a  burette  until  the  liquid 
becomes  blue  ;  the  amount  of  arsenic  corresponding  with  i  c.c.  of  the 
iodine  solution  is  then  calculated. 

Procedure.  Into  a  distillation  flask  (about  |  litre)  furnished  with  a 
lateral  bulb-tube  are  introduced  5  grams  of  the  sample,  3-5  grams  of  powdered 
potassium  chlorate  and  then,  gradually  and  with  shaking  and  cooling,  80 

1  Some  authors  dispense  with  the  current  of  hydrogen  during  the  attack  of  the 
metal  and  merely  drive  the  air  from  the  apparatus  before  the  action  and  displace  the 
pr  oducts  of  the  reaction  when  the  metal  is  completely  dissolved,  by  means  of  a  current 
of   carbon  dioxide. 

2  The  iodine  solution  used  for  the  volumetric  determination  of  the  sulphur  (see  p, 
177)  is  suitable  ;    or  3-3858  grams  of  iodine  and  10  grams  of  potassium  iodide  may  be 
dissolved  to  i  litre,  i  c.c.  of  this  solution  corresponding  with  i  m.  grm.  of  arsenic. 


i8o 


IRON 


c.c.  of  hydrochloric  acid  (D  =  1-19).  When  the  action  slackens,  the  flask 
is  heated  carefully  on  a  water-bath  until  the  smell  of  chlorine  disappears 
and,  when  cold,  200  c.c.  of  hydrochloric  acid  (D  1-19)  and  50  grams  of 
ferrous  chloride  or,  better,  25-30  grams  of  cuprous  chloride,  free  from  arsenic, 
are  added. 

To  the  neck  of  the  distilling  flask  is  fitted,  by  means  of  two  grey  rubber 
stoppers,  an  internal  pressure  regulator,  consisting  of  an  inverted  flask 
rather  less  than  half  filled  with  concentrated  hydrochloric  acid  and  fitted 

with  tubes  t  and  t1  of  about  6 
mm.  bore  (see  Fig.  14)  which,  if 
the  pressure  falls,  allow  air  to 
enter  the  flask  and  rapidly  to  re- 
establish the  equilibrium.  The 
concentrated  hydrochloric  acid  in 
the  regulating  flask,  as  it  gradu- 
ally becomes  heated,  further  tends 
to  increase  the  pressure  and  thus 
contributes  to  the  regularity  of 
the  distillation. 

The  side-tube  of  the  distill- 
ing flask — provided  with  a  small 
bulb  to  prevent  drops  spurted 
from  the  boiling  liquid  from  ris- 
ing along  the  side-tube — is  then 
connected  with  a  100  c.c.  pipette, 
which  dips  for  a  few  millimetres 
into  boiled  water  rendered  alka- 
line with  50-60  c.c.  of  ammonia 
(D  0-91)  and  mixed  with  a  few 
drops  of  methyl  orange,  this  being 
contained  in  a  moderately  large 
beaker  standing  in  a  bath  of  cold 


FIG.  14 


water.  The  flask  is  then  heated 
and  most  of  the  liquid  contained 
in  it  slowly  distilled  until  the  solution  in  the  beaker,  becoming  acid, 
assumes  a  faintly  red  colour. 

At  this  point  the  pipette  is  removed  and  rinsed  out  with  a  little  water, 
the  distillate  being  rendered  alkaline  by  a  slight  excess  of  powdered  sodium 
bicarbonate,  mixed  with  a  little  starch  paste  and  titrated  with  the  iodine 
solution  ;  the  proportion  of  arsenic  in  the  metal  is  thus  ascertained. 

*** 


Cast-irons  always  contain  marked  quantities  of  impurities  ;  they  are  brittle 
and  non-malleable. 

Grey  cast-irons  are  more  or  less  dark  in  colour  according  to  their  content 
in  graphitic  carbon,  and  they  have  a  granular  structure,  melt  at  about  1200° 
and  have  the  specific  gravity  7-0-7-2.  They  contain  considerable  proportions 
of  silicon  (from  i%  in  the  paler  products  to  3-5%  in  the  darker  ones,  the  mean 


IRON 


181 


being  1-5-2%).  They  are  very  rich  in  carbon  (2-5%),  which  occurs  entirely 
in  the  graphitic  state  in  ordinary  grey  cast-irons,  and  partly  combined  in  the 
lighter  ones.  They  contain  also  small  quantities  of  manganese  (about  i%)  and 
sometimes  sulphur  (o-oi-o-i%)  and  phosphorus  (0-05-1-8%).  They  serve  in 
general  for  foundry  purposes  and  those  with  little  phosphorus  for  refining. 

White  cast-irons  have  a  shining,  white  colour  tending  to  grey,  a  crystalline, 
granular  and,  sometimes,  radiating  fibrous  structure  ;  they  melt  at  about  1100° 
and  have  the  specific  gravity  7'4~7'5-  They  contain  2-3-5%  of  carbon,  largely 
combined,  and  only  small  quantities  of  silicon  (0-5-1%),  but  they  are  very  rich 
in  manganese  (1-5%),  and  sometimes  contain  considerable  proportions  of  sul- 
phur (0-1-0-25%)  and  phosphorus  (more  than  3%).  They  are  usually  employed 
for  refining. 

The  products  containing  more  than  5%  of  manganese  are  :  Spiegeleisen  (5-30% 
Mn,  0-2-1-2%  Si  and  4-5%  C),  Silico-spiegel  (20%  Mn,  10-12%  or  even  more  Si), 
and  Ferro-manganese  (30-85%  Mn  and  up  to  7-5%  C). 

Malleable  iron  represents  the  product  of  the  refining  of  cast-iron,  contains 
less  than  2%  of  carbon  and,  according  to  its  carbon  content,  to  its  uses,  and  to 
its  hardness,  elasticity,  strength,  etc.,  is  subdivided  into  :  soft  iron  (soft  wrought- 
iron  or  mild  steel,  according  to  the  mode  of  preparation),  which  is  very  ductile 
and  malleable  and  contains  less  than  0-3-0-5%  of  carbon  ;  and  steel  (cementa- 
tion or  blister  steel,  crucible  steel,  cast  steel,  etc.),  which  has  larger  amounts  of 
carbon  (more  than  0-3-0-5%)  and  is  ductile  and  malleable,  but  very  hard,  elastic 
and  resistant  and  capable  of  being  hardened.  Steels  with  more  than  1-5% 
of  carbon  begin  to  lose  their  malleability  and  become  brittle. 

Small  quantities  of  silicon  increase  the  hardness  of  malleable  iron  but  dimin- 
ish its  malleability  (a  good  malleable  iron  should  not  contain  more  than  o-i— 
0-2%).  Most  harmful  for  malleable  iron  are  phosphorus,  which  even  in  small 
quantities  (0-1%)  renders  it  cold  short,  and  sulphur,  which  renders  it  red  short 
even  in  the  proportion  of  0-05-0-1%.  Manganese  diminishes  the  harmful 
effects  of  sulphur  and  hence  improves  the  quality  of  iron  and  steels.  Injuri- 
ous actions  are  also  exerted  by  arsenic,  tin,  antimony,  copper  (beyond  0-4%), 
oxygen,  etc. 

The  following  table  gives  the  compositions  of  various  commercial  types  of 
soft  iron  and  steel. 


TABLE   VIII 
Compositions  of  Various  Iron  and  Steels  (percentages) 


C 

Si 

Mn 

P 

S 

Swedish  iron 

0-02-0-07 

<^O-OI-O-O2 

0-0-15 

Trace-o-o2 

O-OI-O-O2 

Wrought-iron   . 

0-16 

O-O2 

0-09 

0-09 

Trace 

Wrought  steel  . 

0-90 

o-io 

0-25 

0-07 

Trace 

Ingot  iron  for  construc- 

tion      

0-08-0-25 

<^0-O2 

0-4-0-6 

<Vo8 

<o-o8 

Ingot  steel  for  rails 

0-30-0-50 

O-O5-O-20 

0-5-1-0 

<o-o8 

<o-o8 

Martin  steel  for  castings 

0-30-0-60 

O'2O-O-6O 

0-5-1-0 

o-i 

— 

Crucible  tool  steel  . 

0-7-1-2 

0-I-O-2 

0-1-0-3 

<0-04 

<o-03 

182  SPECIAL  STEELS 

SPECIAL  STEELS 

Special  or  high-speed  steels,  now  largely  used,  are  characterised  by  the 
presence  of  some  suitable  element,  such  as  chromium,  tungsten,  nickel, 
etc.,  which  confers  quite  special  properties.  The  chemical  analysis  of 
special  steels  includes,  therefore,  besides  the  ordinary  determinations,  those 
of  the  specific  elements  present.  Tests  will  first  be  given  for  the  identifi- 
cation of  these  elements. 

Qualitative  Tests 

• 

1.  Detection  of  Chromium. — A  litt1^  of  the  finely  powdered  sample 
is  heated  on  the  cover  of  a  platinum  crucib     or  in  a  porcelain  dish  and  the 
residue  fused  with  sodium  carbonate  and  nit*        In  presence  of  chromium 
a  more  or  less  intensely  yellow  mass  is  obtained,     i ."  a  solution  (which  should 
be  acid)  of  this  in  dilute  acetic  acid  is  treated  with  silver  nitrate,  a  brick- 
red  precipitate  is  obtained. 

2.  Detection  of  Nickel. — A  little  of  the  sample  is  dissolved  in  hydro- 
chloric acid,  the  iron  oxidised  with  nitric  acid  and  a  little  tartaric  acid  (2 
grams  per  0-5  gram  of  the  steel)  dissolved  in  a  little  water  added.     The 
liquid  is  then  made  alkaline  with  ammonia  and  heated  with  a  little  i% 
solution  of  dimethylglyoxime  in  alcohol :   a  red  precipitate  indicates  nickel. 

3.  Detection   of   Manganese. — (a)  A   little   of  the   finely  powdered 
sample  is  heated  on  a  platinum  crucible  cover  or  in  a  porcelain  dish  and 
the  residue  fused  with  sodium  carbonate  and  nitre,     (b)  The  sample  is 
treated  with  nitric  acid  (D  1-2)  and  the  solution  heated  with  a  little  lead 
peroxide  free  from  manganese.     When  the  peroxide  settles,  the  liquid  will 
exhibit  a  violet- red  colour  if  manganese  is  present.     This  reaction  is  very 
sensitive  and  with  ferro-manganese,  a  very  small  quantity  must  be  taken. 

4.  Detection  of  Tungsten. — A  little  of  the  finely  powdered  sample 
is  fused  with  sodium  carbonate  and  nitre,  the  mass  being  taken  up  in  hot 
water  and  the  solution  filtered,  acidified  strongly  with  hydrochloric  acid 
and  heated.     In  presence  of  tungsten,  a  white  precipitate  is  obtained,  turning 
yellow  on  heating ;   this  consists  of  anhydrous  tungstic  acid  and  is  soluble 
in  sodium  carbonate. 

5.  Detection  of  Vanadium. — A  little  of  the  sample  is  dissolved  in 
nitric  acid  (D  =  1-18)  and  a  small  quantity  of  hydrogen  peroxide  allowed 
to  flow  down  the  side  of  the  tube.     In  presence  of  vanadium,  a  reddish- 
brown  coloration  is  formed  at  the  zone  of  contact  of  the  two  liquids. 

6.  Detection  of  Molybdenum.— A  little  of  the  finely  powdered  sample 
is  heated  and  the  residue  fused  with  sodium  carbonate  and  nitre,  the  mass 
being  treated  with  hot  water  and  filtered.     The  filtrate  is  strongly  acidified 
with  sulphuric  acid,  evaporated  and  heated  until  white  fumes  appear.     A 
little  cone,  sulphuric  acid  is  stirred  into  the  cold  liquid  and,  without  diluting, 
alcohol  is  added.     In  presence  of  molybdenum  an  intense  blue  coloration 
is  obtained.     This  coloration  disappears  on  dilution  with  water,  and  if  the 
liquid  is  then  subjected  in  the  hot  to  the  action  of  hydrogen  sulphide,  a 
brown  precipitate  of  molybdenum  sulphide  is  obtained. 


CHROME  STEELS  183 

7.  Detection  of  Silicon. — The  sample  is  ground  with  sodium  carbonate 
and  nitre  and  the  mass  dissolved  in  dilute  hydrochloric  acid  and  evaporated 
to  dryness.     After  being  heated  for  an  hour  in  an  oven  at  120-130°,  the 
residue  is  treated  with  hot  dilute  hydrochloric  acid  and  filtered.     In  presence 
of  silicon,  a  more  or  less  abundant  residue  of  silica,  attackable  by  hydro- 
fluoric acid,  remains.     Ferro-silicon  with  a  high  proportion  of  silicon  is 
dissolved  in  10%  sodium  hydroxide  solution. 

8.  Detection  of  Titanium. — A  little  of  the  sample  is  dissolved  in. 
nitric  acid  and  evaporated  to  dryness,  the  residue  being  ignited  to  decom- 
pose nitrates.     The  oxides  thus  obtained  are  fused  with  bisulphate,  the 
cooled  mass  being  dissolved  in  cold  water,  acidified  with  sulphuric  acid 
and  treated  with  hydrogen  peroxide.     In  presence  of  titanium  a  distinctly 
yellow  coloration  is  exhibited. 

9.  Detection  of  Aluminium. — A  little  of  the  sample  is  dissolved  in 
hydrochloric  acid  diluted  with  an  equal  volume  of  water,  a  few  drops  of 
nitric  acid  being  added  (to  oxidise  the  iron),  the  liquid  rendered  alkaline 
with  sodium  hydroxide,  diluted,  boiled  for  some  time  and  filtered.     When 
the  filtrate  is  heated  with  excess  of  ammonium  chloride,  a  gelatinous  pre- 
cipitate of  aluminium  hydroxide  is  obtained  if  aluminium  is  present. 

CHROME    STEELS 

Chrome  steels  are  hard  and  highly  resistant  to  ordinary  acids,  and 
are  used  particularly  for  the  manufacture  of  tools,  projectiles,  cylinders, 
etc.  Their  analysis  includes,  besides  the  ordinary  determinations,  that  of 
chromium. 

1.  Determination  of  the  Chromium. — The  commonest  methods  for 
estimating  chromium  in  steels  consist  in  transforming  the  chromium  into 
chromic  acid  or  alkaline  chromate  and  in  determining  the  latter  volumetri- 
cally.  Owing  to  its  accuracy  and  rapidity,  the  iodometric  method  is  to 
be  recommended.  In  presence  of  vanadium  and  molybdenum,  which 
often  accompany  chromium  in  steels,  the  method  is  slightly  modified  to 
get  rid  of  these  metals,  which  behave  towards  iodine  as  chromium  does. 

Reagents  :  (i)  N/io-potassium  dichromate  solution,  prepared  by  dis- 
solving 4-9033  grams  of  the  salt — recrystallised  in  small  crystals  and  dried 
at  130° — in  water  to  i  litre. 

(2)  Approximately  N/io-sodium  thiosulphate,  25  grams  being  dissolved 
to  i  litre. 

(3)  Starch  paste. 

Titration  of  the  thiosulphate.  To  establish  the  titre  of  the  thiosulphate 
solution  with  respect  to  the  dichromate,  and  hence  with  respect  to  chromium, 
20  c.c.  of  the  dichromate  solution  (corresponding  with  0-09806  gram  of 
dichromate)  are  measured  out,  and  10  c.c.  of  10%  potassium  iodide  (free 
from  iodate)  1  solution  and  5  c.c.  of  hydrochloric  acid  (D  i-i)  added,  the 
liquid  being  then  shaken  and,  after  addition  of  200—250  c.c.  of  water,  titrated 
with  the  thiosulphate  solution  ;  starch  paste  is  added  towards  the  end  of 

1  An  aqueous  solution  of  the  potassium  iodide,  acidified  with  hydrochloric  acid 
and  mixed  with  a  little  starch  paste,  should  remain  colourless. 


184  CHROME  STEELS 

the  titration.     The  volume  of  thiosulphate  used  corresponds  with  0-09806 
gram  of  potassium  dichromate,  and  hence  with  0-03466  gram  of  chromium. 

(a)  DETERMINATION    OF   THE   CHROMIUM   IN   ABSENCE    OF   VANADIUM 
AND  MOLYBDENUM.    2  grams  of  the   sample,  in   a   small   porcelain   dish 
covered  with  a  clock-glass,  are  dissolved  in  nitric  acid  of  D  =  1-18  and  the 
solution  evaporated  to  dryness  and  the  residue  ignited  to  decompose  the 
nitrates.     When  cold,   the  oxides  are  transferred  quantitatively  with  a 
platinum  spatula  to  an  agate  mortar  in  which  they  are  mixed  with  sodium 
peroxide,  the  dish  being  repeatedly  cleaned  in  the  dry  with  small  quantities 
of  the  peroxide  (of  which  not  more  than  10-15  grams  should  be  used  alto- 
gether).    The  last  traces  of  oxides  adherent  to  the  dish  are  removed  by 
heating  with  a  little  dilute  sodium  hydroxide  solution,  the  alkaline  solution 
together  with  the  water  used  to  wash  out  the  dish  being  transferred  to  a 
beaker. 

The  peroxide  mixture  is  heated  gently  to  fusion  in  a  covered  nickel  or 
porcelain  crucible,  the  heating  being  then  continued  for  about  15  minutes 
at  dull  red  heat.  The  cold  crucible  is  treated  in  a  covered  beaker  with 
hot  water  in  which  the  mass  rapidly  dissolves,  the  alkaline  liquid  used  for 
the  final  washing  of  the  dish  being  then  added,  the  crucible  withdrawn 
and  washed  and  the  beaker  kept  for  1-2  hours  on  a  steam-bath.  If  the 
solution  appears  greenish,  owing  to  the  presence  of  manganates,  the  latter 
are  reduced  by  addition  of  a  little  sodium  peroxide.  The  liquid  is  then 
made  up  to  about  200  c.c.,  allowed  to  cool  and  filtered  by  decantation,  the 
filtrate  being  collected  in  a  500  c.c.  flask  and  the  residue  washed  repeatedly 
with  dilute  sodium  carbonate  solution.1  When  the  washing  is  completed, 
the  filtrate  is  boiled  to  decompose  any  traces  of  sodium  peroxide  still  present 
and,  after  cooling,  made  up  to  volume. 

To  100  c.c.  of  this  solution  (0-4  gram  of  the  sample),  acidified  with  hydro- 
chloric acid,  are  added  10  c.c.  of  10%  potassium  iodide  solution,  the  liquid 
being  then  diluted  to  200-300  c.c.  and  the  free  iodine  titrated  with  thio- 
sulphate as  before. 

(b)  DETERMINATION  OF  THE  CHROMIUM   IN   PRESENCE   OF  VANADIUM 
AND  MOLYBDENUM.     When  the  oxidation  of  the  chromium  by  fusion  with 
sodium  peroxide  (see  a,  above)  is  complete,  the  aqueous  extract — which 
may  contain  alkaline  vanadates  and  molybdates  in  addition  to  chromate — is 
neutralised  exactly  with  nitric  acid  (towards  methyl  orange),  heated  to 
boiling  and  treated  with  a  slight  excess  of  10%  mercurous  nitrate  solution. 
Under  these  conditions  the  chromium,  vanadium,  molybdenum,  tungsten 
and  phosphorus  are  precipitated. 

The  liquid  is  heated  to  boiling  and,  when  the  precipitate  has  settled, 
mercurous  nitrate  solution  is  added  to  ascertain  if  the  precipitation  is  com- 
plete. In  case  the  solution  has  become  acid,  it  is  neutralised  with  a  few 
drops  of  ammonia  and  filtered,  the  precipitate  being  washed  first  with 
water  and  then  with  very  dilute  mercurous  nitrate  solution.  The  filter 
and  the  whole  of  the  precipitate,  in  an  open  platinum  crucible,  are  then 

1  If  traces  of  chromium  still  remain  in  the  residue,  the  latter  is  fused  with  sodium 
and  potassium  carbonates,  the  resulting  product  extracted  and  the  new  solution  added 
to  that  of  the  first  treatment. 


CHROME  STEELS  185 

incinerated  in  an  efficient  draught-chamber  to  expel  the  mercury.  The 
residue  is  strongly  ignited,  allowed  to  cool,  mixed  in  the  crucible  with  8-10 
parts  of  a  mixture  of  4  parts  of  sodium  carbonate  with  I  part  of  potassium 
bitartrate,  and  heated  carefully  so  as  not  to  burn  the  carbonaceous  residue 
entirely  away. 

The  chromium  then  remains  as  oxide,  whilst  the  vanadium,  molybdenum 
and  tungsten  form  the  sodium  salts  of  the  respective  acids.  The  crucible 
is  next  heated  with  water  in  a  beaker,  the  crucible  extracted  and  the  in- 
soluble residue  of  chromic  oxide  and  carbon  filtered  off,  washed  first  with 
water  containing  a  little  sodium  carbonate  and  then  with  water  acidified 
with  nitric  acid,  dried  and  ignited  in  a  tared  platinum  crucible.  The  chromic 
oxide  thus  obtained  may  be  weighed  directly.  The  result  may  be  con- 
trolled volumetrically  by  heating  the  oxide  with  a  mixture  of  sodium  car- 
bonate and  magnesium  oxide  (see  Ferro-silicon),  dissolving  the  resultant 
mass  in  hydrochloric  acid,  making  up  to  volume  in  a  500  c.c.  measuring 
flask  and  titrating  the  chromium  in  an  aliquot  part  (see  i,a). 

2.  Determination  of  the  Carbon,  Silicon,  Phosphorus,  Sulphur 
and  Arsenic. — The  methods  used  for  ordinary  steels  are  applicable  (see 
Iron,  i,  2,  4,  5  and  6). 

3.  Determination  of  the  Manganese. — The  residue  remaining  undis- 
solved  on  lixiviation  of  the  fused  mass  (see  I,  a]  is  dissolved  in  hydrochloric 
acid  and  the  manganese  determined  in  this  solution,  which  contains  also 
all  the  iron  (see  Ferro-silicon,  3). 


* 
*  * 


Chrome  steels  may  contain  0-3-4%  of  chromium  (usually  1-2%),  0-3-1-6% 
of  carbon,  0-05-0-3%  of  silicon,  0-5-1%  of  manganese,  and  traces  of  phosphorus 
and  sulphur  (0-01-0-04%).  Extra  hard  steels  contain  2-3%  of  chromium  and 
1-5-1-6%  of  carbon.  Nickel,  vanadium,  tungsten,  silicon,  etc.,  are  often  asso- 
ciated with  the  chromium  (chrome-nickel,  chrome- vanadium,  chrome-tungsten, 
chrome-silicon,  etc.,  steels). 

It  should  be  noted  that  small  proportions  of  chromium  (less  than  0-1%)  are 
found  in  almost  all  ordinary  steels. 

The  following  table  gives  the  percentage  compositions  of  some  commercial 
samples  of  chrome  steels  (Geiger)  : 


TABLE  IX 
Composition  of  Chrome  Steels 


No. 

C 

Si 

Mn 

P 

S 

Cr 

I          ... 

0-311 

0-149 

0-98 

0-039 

0-031 

0-361 

2           ... 

0-382 

0-279 

1-03 

0-035 

0-042 

1-045 

3        ... 

0-895 

0-280 

0-97 

0-018 

0-014 

0-480 

186  NICKEL  STEELS 


NICKEL    STEELS 

Nickel  steels  are  valued  particularly  on  account  of  their  strength  and 
elasticity. 

Their  analysis  includes  determinations  of  the  usual  elements  of  ordinary 
steels  and  also  of  the  nickel  and,  sometimes,  chromium  and  tungsten. 

1 .  Determination  of  the  Nickel  by  means  of  Dimethylglyoxime. — 
In  a  solution  which  is  either  ammoniacal  or  faintly  acid  with  acetic  acid, 
dimethylglyoxime  precipitates  nickel  quantitatively  as  nickeloxime  ;    this 
is  a  red,  crystalline  precipitate  which  can  readily  be  collected  on  a  Gooch 
crucible,  washed  and  weighed. 

Procedure.  With  steels  containing  less  than  3%  Ni,  2  grams,  or  pro- 
portionately less  with  richer  steels,1  are  treated  in  a  porcelain  dish,  covered 
with  a  clock-glass,  with  nitric  acid  (D  1-2).  The  solution  is  evaporated 
to  dryness  and  the  residue  calcined  and  taken  up  in  hydrochloric  acid  as 
indicated  for  the  determination  of  silicon  in  steels  and  cast-iron  (see  p.  172 ) . 

To  the  hydrochloric  acid  solution,  freed  from  silica  and  diluted  to  250— 
300  c.c.,  are  added  about  7  grams  of  tartaric  acid  dissolved  in  a  little  water 
for  each  gram  of  metal  taken,  the  liquid  being  then  rendered  alkaline  with 
dilute  ammonia  so  as  to  give  a  perfectly  clear  solution. 

The  latter  is  then  again  slightly  acidified  with  hydrochloric  acid,  heated 
almost  to  boiling  and  10-20  c.c.  of  a  i%  solution  of  dimethylglyoxime  in 
alcohol  (0-05  gram  of  nickel  requires  about  20  c.c.)  added  drop  by  drop 
and  with  shaking  ;  ammonia  is  then  added  until  the  liquid  just  smells  dis- 
tinctly. The  nickel  is  separated  as  a  voluminous,  crystalline  precipitate. 
After  a  few  minutes,  5-10  c.c.  of  the  dimethylglyoxime  are  added  to  ascertain 
if  the  precipitation  is  complete,  and  when  this  is  so  the  liquid  is  heated  for 
about  30  minutes  on  a  water-bath  and,  when  cold,  filtered  through  a  Gooch 
crucible.  The  precipitate  is  washed  repeatedly  with  hot  water,  dried  at  120° 
and  weighed  ;  the  weight  obtained,  multiplied  by  0-2032  gives  the  amount 
of  nickel  in  the  sample  taken.2 

2.  Determination   of  the  Carbon,   Phosphorus,   and   Sulphur.— 
See  Iron,  i,  4,  5. 

3.  Determination   of  the  Silicon. — The  silica  separating  when  the 
metal  is  treated  with  nitric  acid,  is  weighed  (see  above  and  Iron,  2). 

4.  Determination  of  the  Manganese. — -In  presence  of  small  quan- 
tities of  nickel,  the  manganese  may  be  determined  by  Volhard's  volumetric 
method  (see  p.  197). 

If,  however,  nickel  is  present  in  large  quantities,  the  sample  is  dissolved 
in  hydrochloric  acid  and  the  iron  eliminated  by  treatment  with  ether  in 
Rothe's  apparatus,  the  nickel  being  then  separated  from  the  manganese  by 
means  of  ammonia  and  bromine  water. 

1  For  steels  with  10-25%  of  nickel,  it  is  advisable  to  use  i  gram  and,  after  elimina- 
tion and,  if  required,  estimation  of  the  silica,  to  make  up  to  a  definite  volume  and  take 
an  aliquot  part  containing  about  0-05  gram  of  nickel  for  the  determination. 

2  For  the  volumetric  determination  of  nickel  in  steels,  see  Belasio  and  Marchion- 
neschi,  Annali  di  Chim.  Applicata    1914,  I,  p.  133. 


MANGANESE  STEELS 


187 


5.  Determination    of   the   Chromium.  —  See   Analysis    of   Chrome- 
nickel  Steels. 

6.  Determination  of  the  Tungsten.  —  The  tungsten  is  first  separated 
as  tungstic  acid  on  the  lines  indicated  for  the  analysis  of  tungsten  steels 
(see  p.  1  88)  and  the  nickel  in  the  filtrate  estimated  by  the  method  given 
above. 


Nickel  steels  usually  contain  0-5-10%  Ni  but  the  content  may  reach  25%, 
especially  in  steels  for  armour-plating,  or  even  more  (invar  contains  46%  Ni 
and  0-15%  C).  Chromium  is  often  associated  with  the  nickel  (chrome-nickel 
steels)  . 

The  following  results  are  given  by  Geiger  : 


TABLE   X 
Composition  of  Nickel  Steels  (percentages) 


Nickel  Steel  for 

C 

Si 

Mn 

P 

Si 

Ni 

Ball  mills  

0-07 

0-345 

0-65 

0-045 

0-057 

0-246 

Brakes  

0-361 

0-280 

0-68 

0-023 

0-035 

3-85 

Gun  barrels  (American)  . 

o-39 

0-197 

o-75 

O-O2 

0-032 

2-62 

Toothed  wheels     .... 

0-25 

0-216 

0-52 

O-OII 

0-019 

i-85 

MANGANESE    STEELS 

Manganese  steels  are  valued  for  their  hardness  and  strength,  and  have 
properties  analogous  to  those  of  nickel  steels  and  are  less  costly.  From 
the  analytical  standpoint  they  may  be  regarded  as  ordinary  steels  very  rich 
in  manganese. 

1.  Determination  of  Silicon   and   Manganese. — 2-5  grams  of  the 
sample  are  treated  with  nitric  acid  (D  1-18)  and  the  liquid  evaporated  to 
dryness,  calcined,  and  taken  up  in  hydrochloric  acid,  the  solution  being 
again  evaporated  and  the  residue  heated  at  135°  to  render  the  silica  com- 
pletely insoluble.     The  subsequent  procedure  is  as  indicated  on  p.  172. 

The  filtrate  is  collected  in  a  measuring  flask  and  the  manganese  present 
determined  either  by  Volhard's  volumetric  method  or  electrolytically  (see 
later,  Ferro-manganese) . 

2.  Determination   of  the   Carbon,   Phosphorus   and   Sulphur. — 
See  Iron,  i,  4,  5. 

* 
*  * 


The  percentage  compositions  of  certain  manganese  steels  in  common  use  are 
(Geiger)  : 


i88 


TUNGSTEN  STEELS 


TABLE   XI 
Composition  of  Manganese  Steels 


No. 

C 

Si 

Mn 

P 

S 

I   . 

0-320 

0-311 

6-32 

0-077 

0-036 

2    . 

0-585 

0-265 

9-61 

0-086 

0-042 

3  •      • 

0-804 

0-280 

8-70 

0-034 

0-015 

4  •      • 

1-085 

0-241 

12-24 

0-068 

0-012 

TUNGSTEN    STEELS 

Tungsten  steels  are  very  hard  and  serve  specially  for  making  tools, 
permanent  magnets,  etc.  Their  analysis  includes  estimations  of  the 
ordinary  elements  of  steel  and  also  of  tungsten. 

1.  Determination  of  the  Silicon  and  Tungsten. — When  tungsten 
steel  is  treated  with  nitric  acid,  the  silicon  present  separates  as  silica  and 
the  tungsten  as  tungstic  acid.  After  weighing,  the  precipitate  is  treated 
with  hydrofluoric  acid,  the  loss  representing  the  silica  and  the  remainder 
the  tungstic  acid. 

Procedure.  2-5  grams  of  the  finely  powdered  sample  are  treated  in  a 
covered  dish  with  nitric  acid  (D  1-18),  the  solution  being  evaporated  and 
the  residue  ignited  to  decompose  the  nitrates  and  taken  up  in  hydrochloric 
acid.  The  liquid  is  then  evaporated  to  dryness,  the  silica  rendered  insoluble 
at  135°,  as  under  2,  p.  172.  The  residue  is  moistened  with  cone,  hydro- 
chloric acid  and  then  just  sufficient  hydrochloric  acid  (D  1-12)  added  to 
dissolve  the  ferric  oxide  in  the  hot.  The  liquid  is  evaporated  to  a  syrup, 
allowed  to  cool,  diluted  with  about  double  its  volume  of  water  acidified 
with  hydrochloric  acid  and,  after  a  few  minutes,  filtered  by  decantation. 
The  precipitate  is  afterwards  introduced  on  to  the  filter  and  washed  with 
water  acidified  with  hydrochloric  acid  until  the  liquid  passing  through  no 
longer  gives  the  reaction  for  iron  with  thiocyanate.1  After  being  dried, 
the  filter  and  precipitate  are  incinerated  in  a  platinum  crucible  and  the 
residue  ignited  at  not  too  high  a  temperature  (not  in  the  blowpipe  flame) 
and  weighed. 

To  eliminate  and  estimate  the  silica,  the  weighed  mixture  of  tungstic 
acid  and  silica  is  treated  with  a  little  sulphuric  acid  and  a  few  c.c.  of  hydro- 
fluoric acid  and  the  procedure  indicated  on  p.  171  then  followed. 

The  loss  of  weight  gives  the  silica  and  this,  multiplied  by  0-4693  the 
silicon  ;  the  residue  is  the  tungstic  acid,  multiplication  by  0-7931  giving  the 
tungsten. 

If  the  sample  contains  more  than  10-15%  of  tungsten,  it  is  difficult 
to  attack  with  nitric  acid  and  it  is  then  advisable  to  have  recourse  to  fusion 
(see  later:  Ferro-tungsten). 

1  A  yellow  ring  of  tungstic  acid,  difficult  to  remove  merely  by  washing,  is  often 
formed  in  the  dish.  This  may  be  detached  by  gentle  rubbing  with  a  piece  of  filter  paper 
moistened  with  ammonia,  the  paper  being  then  added  to  the  rest  of  the  precipitate. 


VANADIUM  STEELS  189 

Further,  there  are  some  types  of  tungsten  steel,  especially  the  chrome- 
tungsten  steels,  which,  although  they  have  not  a  high  content  of  tungsten, 
are  difficult  to  dissolve  in  nitric  acid.  In  such  cases,  when  the  action  of 
the  nitric  acid  ceases,  a  few  drops  of  cone,  hydrochloric  acid  are  added,  this 
being  repeated  until  the  attack  of  the  metal  is  complete. 

The  tungstic  acid  freed  from  silica  may  often  contain  small  amounts 
of  iron  and  chromium.  In  this  event,  the  weighed  residue  is  fused  with 
sodium-potassium  carbonate,  the  mass  treated  with  hot  water  and  the 
insoluble  residue,  consisting  of  ferric  oxide,  filtered  off,  washed,  ignited  and 
weighed.  The  chromium  is  determined  volumetrically  in  the  filtrate  (see 
p.  183). 

2.  Determination   of  the   Carbon. — For  products  readily  attacked 
by  acids,  the  Corleis  method  may  be  used,  whilst,  for  the  others,  direct 
combustion  in  a  current  of  oxygen  must  be  employed  (see  Iron,  i). 

3.  Determination  of  the  Manganese,  Phosphorus  and  Sulphur.— 
The  determination  of  these  elements  may  be  effected  by  the  methods  de- 
scribed under  Iron,  3,  4  and  5.     For  some  determinations,  such  as  that  of 
the  phosphorus,  use  may  be  made  of  the  hydrochloric  acid  solution  from 
which  the  silica  and  tungstic  acid  have  been  removed. 

* 
*  * 

Tungsten  steels  usually  contain  2-10%  of  tungsten  (but  sometimes  20% 
or  more),  0-5-1-5%  of  carbon,  0-2-0-7%  °f  silicon,  0-4-2-5%  of  manganese  and, 
in  some  cases,  small  quantities  of  phosphorus  ;  a  good  tungsten  steel  should  not, 
however,  contain  more  than  0-015%  °f  phosphorus. 

Cast-and  wrought-iron,  and  ordinary  steels  do  not  usually  contain  tungsten. 


VANADIUM    STEELS 

Owing  to  their  hardness  and  their  resistance  to  shock  and  vibration, 
vanadium  steels  are  used  for  the  framework  of  locomotives,  automobile 
parts,  tools,  etc. 

Their  analysis  includes  estimations  of  the  elements  normally  present 
in  steels  (carbon,  silicon,  manganese,  phosphorus,  sulphur,  etc.)  as  well 
as  that  of  vanadium  and,  sometimes,  of  nickel,  chromium  and  molybdenum, 
which  very  often  accompany  vanadium  in  special  steels. 

1 .  Determination  of  the  Vanadium. — If  the  vanadium  is  transformed, 
by  fusion  with  an  oxidising  agent,  into  vanadic  acid,  it  may  be  determined, 
according  to  Holverscheit,  iodometrically ;  the  vanadic  acid  is  reduced 
by  means  of  hydrobromic  acid,  the  bromine  liberated  in  the  reaction  a 
being  collected  in  potassium  iodide  solution  and  the  iodine  thus  set  free 
titrated  with  thiosulphate. 

Procedure.  2-3  grams  of  the  sample  are  dissolved  in  nitric  acid  (D 
1-18)  in  a  small  porcelain  dish,  the  liquid  evaporated  to  dryness,  the  residue 
ignited  and  the  oxides  obtained  fused  in  a  nickel  crucible  with  12-18  grams 
of  sodium  peroxide,  as  described  for  chrome  steels.  The  mass  obtained 
is  lixiviated  with  hot  water  and  the  residue  insoluble  in  water  dried  and 

=  V2O4  +  H2O  +  Br2. 


igo 


VANADIUM  STEELS 


fused  "with  sodium  carbonate  in  a  platinum  crucible,  this  mass  being  also 

lixiviated  with  water. 

The  two  aqueous  solutions,  which  contain  all  the  vanadium  as  sodium 

vanadate,  are  together  boiled  to  decompose  the  excess  of  peroxide,  evaporated 

to  30-40  c.c.,  and  poured  into  the  flask  of  the  Bunsen  apparatus  (see  Fig. 

15),  the  vessel  being  rinsed  out  with  very  little  water. 

The  alkaline  liquid  is  neutralised  with  cone,  hydrochloric  acid  free  from 

chlorine,  the  yellowish  solution 
being  then  mixed  with  30  c.c. 
of  cone,  hydrochloric  acid  and 
1-3  grams  of  potassium  bro- 
mide. The  apparatus  is  ar- 
ranged as  shown  in  the  figure, 
the  conducting  tube  from  the 
flask  being  dipped  into  the 
potassium  iodide  solution 
(5-10  grams  of  potassium 
iodide  free  from  iodate)  con- 
tained in  the  retort  fixed  so 


FIG.  15. 


as  to  be  rotatable. 

The  liquid  is  then  slowly 
heated  to  boiling,  the  retort  being  turned  at  intervals  to  expel  the 
accumulated  air  ;  the  boiling  is  continued  for  about  10  minutes.  With- 
out interrupting  the  heating,  the  retort  is  removed,  the  conducting  tube 
being  rinsed  with  water.  The  retort  is  then  cooled,  emptied  into  a  beaker 
and  rinsed  out  several  times,  first  with  water  and  then  with  potassium 
iodide  solution.  The  liberated  iodine  is  titrated  with  thiosulphate  in  the 
usual  way :  I  c.c.  N/io-thiosulphate  =  0-005106  gram  of  vanadium.1 

If  the  liquid  from  the  lixiviation  of  the  fused  mass  appears  yellow  owing 
to  the  presence  of  chromates,  it  is  necessary  to  eliminate  the  chromium 
before  titrating  the  vanadium.  After  the  liquid  has  been  boiled  to  decom- 
pose the  excess  of  sodium  peroxide,  it  is  neutralised  exactly  with  nitric 
acid  and  treated  with  mercurous  nitrate  to  precipitate  the  chromium, 
vanadium,  etc.  (see  Analysis  of  Chrome  Steels).  The  precipitate  is  collected 
on  a  filter  and  washed  and  ignited  in  a  platinum  crucible  to  expel  the  mercury, 
the  residue  being  fused  with  sodium  carbonate  and  bitartrate  and  the 
resultant  mass  lixiviated  with  hot  water.  In  the  residue  insoluble  in  water 
the  chromium  is  determined,  and  in  the  alkaline  solution  the  vanadium, 
by  the  method  already  given. 

2.  Determination  of  the  Carbon,  Silicon,  Manganese,  Phosphorus 
and  Sulphur.— See  Analysis  of  Ordinary  Steels  (Iron,  i,  2,  3,  4,  5). 

3.  Determination  of  the  Nickel. — As  in  nickel  steels. 

4.  Determination   of   the    Molybdenum. — When   the   reduction   of 

1  If  the  vanadium  is  present  in  very  small  quantity,  it  is  necessary  to  dissolve  10-15 
grams  of  the  sample  in  hydrochloric  acid,  to  eliminate  the  iron  by  means  of  ether  in 
Rothe's  apparatus,  to  evaporate  the  hydrochloric  acid  solution  containing  the  vanadium 
with  sulphuric  acid  and  to  fuse  the  sulphates  obtained  with  sodium  hydroxide  and 
sodium  peroxide  to  transform  the  vanadium  into  sodium  vanadate. 


MOLYBDENUM  STEELS 


191 


the  vanadic  acid  is  complete,  the  liquid  in  the  flask — which  contains  the 
vanadium  as  vanadyl  salt  and  the  molybdenum  as  molybdic  acid — is  treated 
with  hydrogen  sulphide  in  a  pressure  bottle  ;  the  molybdenum  sulphide 
precipitated  is  collected  in  a  Gooch  crucible,  transformed  into  the  trioxide 
as  in  the  determination  of  molybdenum  in  molybdenum  steels,  and  weighed. 
5.  Determination  of  the  Chromium. — See  above,  p.  190. 

* 
*  * 

The  vanadium  content  of  vanadium  steels  is  usually  about  0-2%  and  scarcely 
ever  exceeds  i%. 

Chromium  and  nickel  are  often  associated  with  the  vanadium,  chrome- 
vanadium,  nickel- vanadium  and  chrome-nickel-vanadium  steels  possessing  the 
valuable  properties  of  vanadium  steels  along  with  those  of  chrome  and  nickel 
steels. 

Small  quantities  of  vanadium  may  be  found  in  ordinary  cast-irons  when 
vanadiferous  ores  have  been  used  for  their  manufacture. 

The  compositions  of  certain  vanadium,  nickel- vanadium,  and  chrome-nickel- 
vanadium  steels  are  as  follows  (Mars,  Geiger)  : 


TABLE   XII 
Composition  of  Vanadium  Steels 


C 

Si 

Mn 

P 

s 

Ni 

Cr 

Va 

Vanadium  steels 

For   locomotive    frame- 
works     
For   tools     and    instru- 
ments     

0-28 
i  -20 

0-28 
0-2O 

o-57 
0-25 

— 

— 

— 

— 

0-22 

o-6-i-o 

Nickel-vanadium  steels 

For  toothed  gearing  for 
automobiles 

0-052 

0-316 

0-67 

O-OI2 

0-028 

6-68 

— 

O-26 

Chrome-nickel-vanadium 
steels 

For  automobile  hubs 

0-068 

0-184 

0-48 

0-O26 

0-033 

572 

1-18 

0-19 

MOLYBDENUM    STEELS 

Molybdenum  steels  are  highly  ductile,  elastic  and  resistant  to  breaking, 
and  are  therefore  mostly  used  for  tools,  although  the  cheaper  tungsten 
steels  are  usually  preferred  for  this  purpose. 

Their  analysis  includes,  besides  determinations  of  the  elements  usual 
in  ordinary  steels  (carbon,  silicon,  manganese,  phosphorus,  sulphur),  also 
that  of  molybdenum  and,  sometimes,  of  tungsten,  chromium,  nickel,  etc. 

1.  Determination  of  the  Molybdenum. — When  the  iron  has  been 
separated  from  the  molybdenum  by  fusion  with  sodium  peroxide  and  lixivia- 
tion  of  the  product  with  water,  the  molybdenum  is  precipitated  in  the 


192  MOLYBDENUM  STEELS 

aqueous  solution  by  hydrogen  sulphide,  the  sulphide  separated  and  ignited 
to  the  trioxide,  which  can  be  purified  if  necessary  and  weighed. 

Procedure.  2-3  grams  of  the  sample  are  treated,  in  a  small,  covered 
porcelain  dish,  with  nitric  acid  (D  =  1-18),  the  solution  evaporated  to  dry- 
ness,  the  residue  ignited  gently  to  decompose  the  nitrates,  and  the  oxides 
obtained  fused  with  sodium  peroxide  in  a  nickel  crucible,  as  indicated  for 
the  analysis  of  chrome  steels.  The  mass  is  lixiviated  with  hot  water,  sodium 
peroxide  being  added  if  the  mass  appears  greenish  owing  to  the  presence  of 
manganates,  and  the  liquid  boiled  and  filtered,  hot  water  being  used  for 
washing. 

The  residue  is  dried  and  fused  with  sodium  carbonate,  and  the  fused 
mass  lixiviated  with  hot  water  to  recover  any  small  quantities  of  molybdenum 
remaining  in  the  residue  insoluble  in  water.  The  two  liquids — which  may 
contain,  besides  the  molybdenum  as  sodium  molybdate,  also  vanadium, 
tungsten,  chromium,  phosphorus,  silicon,  etc. — are  united  and,  if  in  presence 
of  large  quantities  of  molybdenum,  made  up  to  a  definite  volume,  of  which 
an  aliquot  part  is  taken  for  the  determination  ;  where,  however,  the  quantity 
of  molybdenum  is  small,  the  whole  of  the  filtrate  is  taken. 

The  volume  of  the  solution  is  reduced  to  50-60  c.c.,  most  of  the  alkali 
neutralised  with  sulphuric  acid,  25  c.c.  of  concentrated  ammonia  solution 
added  and  the  solution  treated  with  hydrogen  sulphide.  After  some  time 
the  liquid  is  acidified  with  dilute  sulphuric  acid,1  heated  to  boiling  and 
allowed  to  cool,  the  current  of  hydrogen  sulphide  being  continued  through- 
out. The  molybdenum  sulphide  is  filtered  through  a  tared  Gooch  crucible, 
washed  first  with  water  acidified  with  sulphuric  acid  and  then  with  alcohol, 
and  dried  at  100°.  The  crucible,  covered  with  a  clock-glass,  is  placed  in 
a  fairly  roomy  nickel  crucible  and  heated  with  a  small  flame  to  convert  the 
molybdenum  sulphide  into  trioxide.  As  soon  as  the  odour  of  sulphur  dioxide 
ceases,  the  clock-glass  is  removed  and  the  heating  continued  to  constant 
weight,  the  base  of  the  nickel  crucible  being  kept  incandescent. 

The  weight  of  the  molybdenum  trioxide — which  is  pale  yellow  if  pure 
— multiplied  by  0-6667,  gives  the  molybdenum  present. 

In  some  cases  the  molybdenum  trioxide  may  contain  small  quantities 
of  silica.  In  such  case  the  weighed  trioxide  is  dissolved  in  ammonia  in  the 
crucible,  the  residual  silica  being  washed,  dried  and  weighed.  If  vanadium 
is  present  (brown  coloration  of  the  trioxide)  the  weighed  oxides  are  dissolved 
in  a  little  sodium  hydroxide  solution  and  the  vanadium  determined  in  the 
alkaline  solution  (see  Vanadium  Steels),  the  weight  of  the  vanadium  pent- 
oxide  (V2O5)  being  subtracted  from  that  of  the  molybdenum  trioxide  found. 

2.  Determination   of  the   Silicon   and   Tungsten. — The  procedure 
followed  is  that  given  for  estimating  these  elements  in  tungsten  steels. 

3.  Determination  of  the  Carbon,   Manganese,   Phosphorus  and 
Sulphur. — The  methods  used  with  ordinary  steels  are  applicable  (see  Iron, 

i,  3,  4.  5)- 

4.  Determination  of  the  Chromium. — The  chromium  is  estimated 
in  an  aliquot  part  of  the  aqueous  solution  from  the  lixiviation  of  the  mass 

1  If  tungsten  is  present,  acidification  is  preceded  by  addition  of  a  little  tartaric 
acid  to  prevent  the  precipitation  which  would  otherwise  occur. 


CHROME-TUNGSTEN  STEELS  193 

after  fusion  with  sodium  peroxide,  the  method  employed  being  that  given 
on  p.  184  for  the  determination  of  chromium  in  presence  of  molybdenum. 
5.  Determination  of  the  Nickel. — The  method  used  in  the  case  of 
nickel  steels  is  employed. 


Molybdenum  steels  contain  on  the  average  0-5-5%  °*  molybdenum  (rarely 
10-12%),  with  which  chromium,  nickel,  etc.,  are  often  associated,  and  they  con- 
tain the  proportions  of  carbon,  silicon,  phosphorus,  etc.,  normally  present  in 
ordinary  steels. 

Molybdenum  steels  with  3-4%  Mo  and  1-1-5%  C  serve  also  for  making 
permanent  magnets. 

SILICON    STEELS 

Silicon  steels  have  a  very  high  elastic  limit  and  great  resistance  to  shock 
and  are  therefore  used  for  making  springs. 

Their  analysis  includes  essentially  determinations  of  the  silicon  and 
carbon  and  of  the  other  elements  usually  present  in  steels  (Mn,  P,  S,  etc.). 

Each  of  these  determinations  may  be  carried  out  just  as  with  wrought- 

iron,  steel  and  cast-iron  (see  Iron). 

* 
*  * 

The  two  commonest  types  of  silicon  steel  contain  respectively  :  (i)  0-45- 
0-5%  C  and  1-5-1-2%  Si  and  (2)  0-65-0-7%  C  and  0-9-0-8%  Si.  Silicon  steels 
with  2-3%  Si  and  free  from  graphitic  carbon,  are  used  for  dynamo  sheet,  rails, 
etc. 

CHROME-NICKEL    STEELS 

Chrome-nickel  steels  exhibit  the  hardness  of  chrome  steels  and  the 
strength  of  nickel  steels.  They  are  used,  therefore,  for  making  machine 
parts  exposed  to  great  stress,  armour- plating,  projectiles,  etc. 

1.  Determination  of  the  Chromium  and  Nickel. — These  are  esti- 
mated on  two  separate  portions  of  the  sample  by  the  methods  given  for 
chrome  steel  and  nickel  steel. 

2.  Determination  of  the  Carbon,  Silicon,  Manganese,  Phosphorus 
and  Sulphur. — As  with  chrome  steels  and  nickel  steels. 

*** 

Chrome-nickel  steels  for  machine  parts  have  the  following  mean  composition  : 
0-2-0-5%  Cr,  2'5-2>8%  Ni,  0-35%  C  ;  those  for  armour-plating  :  0-2-0-9%  Cr, 
1-7-2-8%  Ni,  0-2-0-4%  C;  and  those  for  projectiles,  0-65-2%  Cr,  2-2-6%  Ni 
and  0-6-0-8%  C. 

CHROME-TUNGSTEN    STEELS 

These  have  the  property  of  retaining  their  temper  even  at  high  tem- 
peratures and  are,  therefore,  used  especially  for  making  tools  for  metal 
working. 

1.  Determination  of  the  Chromium  and  Tungsten. — 2-3  grams 
of  the  sample  are  treated  with  nitric  acid,  evaporated  and  calcined,  the 
oxides  obtained  being  fused  with  sodium  peroxide  as  for  chrome  steels. 
A.C.  13 


194 


CHROME-VANADIUM  STEELS 


The  product  of  the  fusion  is  lixiviated  with  water  and  the  solution  made 
up  to  volume  in  a  measuring  flask.  In  an  aliquot  part  the  chromium  is 
determined  as  indicated  for  the  estimation  of  chromium  in  chrome  steels 
(the  tungstic  acid  present  does  not  interfere  with  the  titration) .  In  another 
aliquot  part  the  chromium  and  tungsten  are  precipitated  with  mercurous 
nitrate  (see  Chrome  Steels),  the  precipitate  being  calcined  to  eliminate  the 
mercury  and  the  residue  of  tungsten  trioxide  and  chromic  oxide  weighed  ; 
the  tungsten  is  thus  obtained  by  difference.  It  is  weh1  to  ascertain  by 
treatment  with  hydrofluoric  and  sulphuric  acids  that  no  silica  is  present 
with  the  chromium  and  tungsten  oxides. 

2.  Determination  of  the  Carbon,  Silicon,  Manganese,  Phosphorus 
and  Sulphur. — As  with  chrome  or  tungsten  steels. 

*  * 

The  percentage  compositions  of  some  of  the  chrome-tungsten  steels  which  are 
most  used  are  : 

TABLE   XIII 
Composition  of  Chrome-tungsten  Steels 


No. 

W 

Cr 

Fe 

C 

Si 

Mil 

I 

I5-5 

4'5 

79-0 

o-43 

0-22 

0-17 

2 

13-5 

8-0 

77-0 

0-60 

0-40 

0-30 

3 

12-0 

3'0 

83-0 

0-71 

O-2O 

O'3O 

4 

9'5 

2-05 

88-0 

°'45 

O-6o 

0-18 

5 

7-0 

2-1 

90-0 

O-2O 

O-25 

0-18 

CHROME-VANADIUM    STEELS 

These  exhibit  all  the  valuable  properties  of  both  vanadium  and  chrome 
steels  and  are  used  for  machine  parts  subjected  to  sudden  stress  and  shock, 
such  as  automobile  parts,  springs,  etc. 

1.  Determination  of  the  Chromium  and  Vanadium. — As  in  vana- 
dium steels  containing  chromium. 

2.  Determination  of  the  Carbon,  Silicon,  Manganese,  Phosphorus 
and  Sulphur. — As  with  chrome  or  vanadium  steels. 

* 
*  * 

The  percentage  compositions  of  certain  types  of  chrome-vanadium  steels  are 
as  follows  (Geiger,  Eschard)  : 

TABLE   XIV 
Composition  of  Chrome-vanadium  Steels 


Used  for 

C 

Si 

Mn 

P 

S 

Cr 

V 

Automobile  framework  . 

0-263 

0-116 

0'43 

0-013 

0-009 

0-934 

0-18 

Drills   

0-518 

0-208 

0-86 

0-027 

0-016 

1-265 

0-16 

Springs      ...... 

O'44 

O-I73 

0-83 

1-044 

0-18 

FERRO-SILICON  195 


FERRO-METALLIC    ALLOYS 

Ferro-metallic  alloys  are  forms  of  cast-iron,  obtained  in  the  blast  furnace 
or  the  electric  furnace  and  containing,  besides  iron,  larger  or  smaller  pro- 
portions of  some  special  element.  They  are  used  for  the  preparation  of 
special  steels  (e.g.,  ferro-chromium,  ferro-tungsten,  etc.)  or  for  the  refining 
of  cast-iron  or  steel  (e.g.,  ferro-silicon,  ferro-aluminium,  etc.).  The  quali- 
tative investigation  of  the  elements  present  is  made  as  with  special  steels 
(see  p.  182). 


FERRO-SILICON 

This  is  generally  prepared  by  fusion  in  the  electric  furnace  of  a  mixture 
of  sand,  coke  and  ferric  oxide,  and  serves  for  the  refining  of  cast-iron  and 
steel.  The  aim  of  the  analysis  is  usually  to  establish  the  percentage  of 
silicon,  but  sometimes  determinations  are  required  of  the  impurities  present, 
e.g.,  carbon,  manganese,  phosphorus,  sulphur,  etc. 

The  types  of  ferro-silicon  on  the  market  nowadays  are  mostly  of  high 
silicon  content  (more  than  25-30%)  and  are  therefore  insoluble  or  incom- 
pletely soluble  in  acids,  so  that  they  must  be  fused  with  alkali. 

1.  Determination  of  the  Silicon. — -Two  methods  are  available: 

(a)  FUSION  WITH  SODIUM  CARBONATE  AND  PEROXIDE. l    An  intimate 
mixture  of  0-3-0-5  gram  of  the  sample  with  12-15  parts  of  sodium  peroxide 
(free  from  silica)  and  6—7  parts  of  anhydrous  sodium  carbonate  is  heated 
in  a  fairly  large,  covered  nickel  crucible,  at  first  very  carefully.     When  the 
reaction  begins  to  slacken,  the  temperature  is  gradually  raised,  the  crucible 
being  heated  round  the  walls  rather  than  at  the  bottom,  so  that  the  mass 
fuses  quietly. 

The  cold  crucible  is  treated  in  a  dish  with  hot  water,  the  crucible  being 
removed  and  washed  and  the  solution,  rendered  distinctly  acid  with  hydro- 
chloric acid,  evaporated  to  dryness  in  a  porcelain  dish.  The  residue  is 
heated  in  an  oven  at  135°  to  render  the  silica  insoluble,  the  subsequent 
procedure  being  as  in  the  determination  of  silicon  in  iron.  In  this  case, 
however,  it  is  necessary  to  evaporate  to  dryness  the  liquid  from  which  the 
silica  has  been  removed  by  filtration  and  to  heat  the  residue  again  at  135° 
to  recover  the  small  quantity  of  silica  always  remaining  in  solution.  In 
the  hydrochloric  acid  solution  the  manganese  and  phosphorus  may  be 
determined  (see  p.  196).  In  this  case  also  it  is  well  to  test  the  purity  of  the 
silica  obtained  by  treatment  with  hydrofluoric  and  sulphuric  acids  as  on 

P-  171- 

(b)  FUSION  WITH  SODIUM  CARBONATE  AND  MAGNESIA.    0*3-1  gram  of  the 
sample,  very  finely  ground  in  an  agate  mortar,  is  mixed  with  about  10  parts 
of  an  intimate  mixture  of  sodium  carbonate  (2  parts)  and  magnesium  oxide 
(i  part),  the  mixture  being  placed  in  a  fairly  large  platinum  crucible,  the 
bottom  of  which  is  covered  with  a  thin  layer  of  the  sodium  carbonate- 

1  The  accuracy  of  the  method  has  been  confirmed   also  by  Namias  ;    Jnd,  Chim, 
Miner,  e  Metatt.,  1915,  II,  p.  281. 


196  FERRO-SILICON 

magnesia  mixture.  The  covered  crucible  is  heated  for  about  an  hour  in 
a  good  bunsen  flame  and  then  for  about  half  an  hour  in  a  blowpipe  flame. 
When  cold,  the  solid  cake  is  placed  in  a  porcelain  dish,  the  crucible 
being  washed  first  with  water  and  then  with  hydrochloric  acid,  the  latter 
being  then  gradually  added  until  the  ferric  and  magnesium  oxides  are  com- 
pletely dissolved  (10  grams  of  the  mixture  require  about  45  c.c.  of  HC1  of 
D  1-12).  The  liquid  is  afterwards  evaporated  to  dryness  and  treated  fur- 
ther as  in  the  preceding  method. 

2.  Determination  of  the  Carbon. — With  products  not  attacked  by 
acids,  the  carbon  should  be  estimated  by  direct  combustion  in  a  current  of 
oxygen  (see  Iron,  i,  b). 

3.  Determination   of  the   Manganese. — (a)  The   hydrochloric   acid 
solution  obtained  in  the  determination  of  the  silicon  as  under  i,  a  or  i,  b  is 
placed  in  a  measuring  flask.     The  residue  remaining  after  treatment  of  the 
silica  with  hydrofluoric  and  sulphuric  acids  is  dissolved  in  hydrochloric 
acid  or,  if  insoluble  matter  then  remains,  fused  with  sodium  carbonate  and 
the  fused  mass  dissolved  in  hydrochloric  acid.     This  solution  is  added  to 
the  other  in  the  measuring  flask,  the  whole  made  up  to  volume  and  the 
manganese  titrated  by  Volhard's  method  (see  Ferro-manganese) . 

(b)  In  presence  of  chromium  or  vanadium,  0-2-2  grams  of  the  sample 
are  fused  with  a  mixture  of  sodium  carbonate  and  magnesium  oxide  (see 
i,b)  and  the  product  lixiviated  with  hot  water  (if  the  mass  is  green  owing  to 
the  presence  of  manganates,  these  are  reduced  by  addition  of  a  small  quantity 
of  sodium  peroxide,  excess  of  which  is  decomposed  by  boiling  for  some  time). 
The  residue  is  collected  on  a  filter,  washed  with  hot  water,  dissolved  in 
cone,  hydrochloric  acid,  boiled  to  expel  chlorine,  and,  when  cool,  made  up 
to  volume  in  a  250  c.c.  measuring  flask  :  in  an  aliquot  part  the  manganese 
is  estimated  by  Volhard's  method  (see  Ferro-manganese). 

4.  Determination  of  the  Phosphorus. — (a)  An  aliquot  part  of  the 
hydrochloric  acid  solution  obtained  after  elimination  of  the  silica  (see  i, 
a  and  b)  is  concentrated  to  a  syrup  and  the  phosphorus  precipitated  with 
the  molybdate  reagent  (see  Determination  of  phosphorus  in  iron). 

(b)  1-3  grams  of  the  sample  are  fused  with  the  sodium  carbonate- 
magnesia  mixture  (see  I,  b),  the  product  being  dissolved  in  hydrochloric 
acid  and  the  silica  rendered  insoluble  and  removed.  The  solution  is  then 
evaporated  to  dryness,  the  residue  dissolved  in  nitric  acid  and  the  phosphoric 
acid  precipitated  with  the  molybdate  reagent. 

5.  Determination  of  the  Sulphur. — 1-3  grams  of  the  sample  are 
fused  with  sodium  carbonate  and  magnesia  (see  i,  b),  the  mass  taken  up 
in  bromine  water,  the  bromine  expelled  by  boiling,  hydrochloric  acid  added 
to  dissolve  the  ferric  oxide  and  magnesia,  the  silica  rendered  insoluble, 
the  residue  taken  up  in  dilute  hydrochloric  acid  and,  the  silica  having  been 
removed,  the  sulphuric  acid  formed  precipitated  in  the  filtrate  with  barium 
chloride  (see  Gravimetric  determination  of  sulphur  in  iron). 


The  more  common,  commercial  ferro-silicons  have  the  following  percentages 
of  silicon  :  20/25,  25/3°>  5°/6o,  -75  and  80/90  ;  those  with  the  higher  propor- 
tions are  the  more  valued. 


FERRO-MANGANESE  AND   SPIEGELEISEN 


197 


As  impurities,  ferrosilicon  contains  small  quantities  of  carbon,  manganese, 
phosphorus,  sulphur  and,  sometimes,  calcium.  Phosphorus  is  an  injurious  con- 
stituent, the  maximum  allowable  limit  being  0-15-0-2%.  The  mean  percentage 
compositions  of  the  commoner  commercial  forms  are  (Geiger)  : 

TABLE   XV 
Compositions  of  Ferro- silicons 


I 

II 

Ill 

IV 

V 

VI 

Silicon        .... 

25-89 

29-66 

51-80 

5375 

51-20 

75-67 

Iron      

72-92 

72-99 

47-30 

45-09 

48-89 

23-01 

Carbon.      .... 

0-52 

— 

0-30 

O-II 

— 

0-31 

Manganese 

0-42 

0-56 

o-35 

o-n 

o-37 

0-26 

Sulphur      .... 

0-03 

o-oi 

O-O2 

0-005 

0-007 

o-oi 

Phosphorus 

0-04 

0-30 

O-O4 

0-041 

0-04 

0-04 

Aluminium 

— 

0-30 

— 

0-60 

0-17 

— 

Chromium. 

— 

.  0-25 



— 

— 

— 

Copper  . 







0-04 

Lime     .      .      .      .      . 

— 

— 



0-05 

O-2I 

— 

FERRO-MANGANESE    AND    SPIEGELEISEN 

Ferro-manganese  is  usually  obtained  in  the  blast  furnace  from  a  mixture 
of  iron  and  manganese  minerals,  and  serves  for  the  de-oxidation  of  steels 
and  for  the  preparation  of  manganese  steels  and  other  special  alloys.  It 
is  slightly  yellowish  white,  compact  and  with  a  granular  structure  inter- 
sected, especially  in  the  high  percentage  types,  by  bluish,  iridescent, 
acicular  crystals. 

Spiegeleisen  is  a  form  of  white  cast-iron  very  rich  in  manganese  with 
a  peculiar  lamellar  structure  and  a  shining  and  sometimes  iridescent  surface  ; 
it  has  the  same  uses  as  ferro-manganese. 

Analysis  of  these  products  may  include,  besides  the  determination  of 
the  manganese,  also  those  of  the  carbon,  silicon,  phosphorus,  sulphur,  etc., 
which  are  always  present  in  the  commercial  products  in  larger  or  smaller 
quantities. 

1.  Determination  of  the  Manganese. — Numerous  methods,  gravi- 
metric, volumetric  and  electrolytic,  have  been  proposed  for  the  determina- 
tion of  the  manganese  in  ferro-manganese  and  manganiferous  cast-irons 
in  general.  The  following  will  be  described  :  Volhard's  volumetric  method 
with  the  recent  modifications  introduced  by  Wolff,  Schoffel  and  Donath, 
and  the  electrolytic  method. 

(a)  VOLUMETRIC  DETERMINATION.  This  method  is  based  on  the  fact  that, 
if  a  neutral  solution  of  a  manganese  salt  is  treated  with  potassium  per- 
manganate, the  whole  of  the  manganese  in  it  is  oxidised  at  the  expense  of 
the  permanganate  and  precipitated,  together  with  that  contained  in  the 
added  permanganate,  as  the  dioxide.  The  manganese  present  is  calculated 
from  the  amount  of  permanganate  necessary  for  the  oxidation. 


198  FERRO-MANGANESE  AND   SPIEGELEISEN 

Reagents,  (i)  Potassium  permanganate  solution  prepared  by  dissolving 
3-2  grams  of  the  pure  salt  in  boiled  distilled  water  and  making  up  to  I  litre. 

(2)  Sodium  arsenite  solution,  obtained  by  dissolving  r6  gram  of  pure 
arsenious  anhydride  and  0-8  gram  of  pure  sodium  hydroxide  in  water, 
heating  if  necessary,  and  making  up  to  i  litre  :  I  c.c.  of  this  solution  corre- 
sponds with  about  0-5  c.c.  of  the  permanganate  solution. 

Tilration  of  the  permanganate  solution  (Sorensen).  About  0-3  gram  of 
pure  sodium  oxalate,  in  minute  crystals  and  dried  at  100°,  is  weighed  exactly, 
dissolved  in  500—600  c.c.  of  boiling  water,  mixed  with  50  c.c.  of  dilute  sul- 
phuric acid  (i  vol.  acid  to  5  vols.  water)  and  the  permanganate  solution 
run  in  from  a  burette  until  a  faint  pink  colour  persists.  Since  670  grams 
of  sodium  oxalate  are  equivalent,  as  regards  permanganate,  to  16479  grams 
of  manganese  as  salt,  the  amount  of  manganese,  x,  corresponding  with  the 
permanganate  used  is  given  by 

670-0  :  164-79  '•'•  P"-  x, 

where  P  is  the  quantity  of  the  oxalate  taken.  The  quotient  of  x  by  the 
number  of  c.c.  of  permanganate  used  gives,  the  amount  of  manganese  corre- 
sponding with  i  c.c.  of  permanganate.1 

Procedure.  1—2  grams  of  ferro-manganese  or  2—5  grams  of  spiegeleisen 
are  treated  with  nitric  acid  (D  =  1-18)  according  to  the  conditions  described 
under  2  (p.  172).  The  solution  is  evaporated,  ignited  to  decompose  the 
nitrates,  taken  up  in  hydrochloric  acid  and  the  silica  rendered  insoluble, 
filtered  and,  if  required,  weighed.  The  hydrochloric  acid  solution,  con- 
taining the  manganese,  when  cold  is  made  up  to  250  or  500  c.c.  in  a  measur- 
ing flask.  The  titration  of  the  manganese  is  carried  out  on  aliquot  parts 
of  the  solution,  each  containing  0-04-0-08  gram  of  manganese. 

If  the  sample  is  of  high  manganese  content  and  hence  contains  too 
little  iron,  it  is  well  to  add  to  each  portion  5—10  c.c.  of  ferric  chloride  solution 
(500  grams  of  pure  ferric  chloride  dissolved  in  water  acidified  with  hydro- 
chloric acid  and  the  volume  made  up  to  i  litre).  In  this  case  it  is  necessary 
to  ascertain,  by  a  blank  test  under  similar  conditions,  whether  the  ferric 
chloride  absorbs  permanganate  and,  if  so,  to  allow  for  this  in  the  calculation. 

Preliminary  test.  Before  titrating,  a  trial  test  must  be  made  to  establish 
the  quantity  of  permanganate  to  be  added. 

An  aliquot  part  of  the  solution  is  treated  in  a  litre  flask  with  a  few  drops 
of  30%  hydrogen  peroxide  to  oxidise  any  trace  of  ferrous  salt  and  then 
heated  to  boiling  to  expel  the  excess  of  the  oxidising  agent.  After  10—15 
minutes'  boiling,  the  volume  is  made  up  to  600-700  c.c.  with  boiling  water, 
a  suspension  of  zinc  oxide  z  in  water  being  then  added  in  small  amounts 
and  with  shaking  until  all  the  iron  is  precipitated  in  brown  flocks  (not  pale 

1  The   reaction   between   sodium   oxalate   and   permanganate   takes    place   thus  : 
5Na2C2O4  +  2KMnO4  +  8H2SO4  =  2MnSO4  +  K2SO4  +  5Na2SO4  +  ioCO2  +  8H2O, 
and  that  between  a  manganese  salt  and  permanganate  in  the  sense, 

3MnCl2  +  2KMnO4  +  2H2O  =  2KC1  +  5MnO2  +  4HC1. 

Hence  2  mols.  of  permanganate  correspond  with  5  of  oxalate  and  with  3  of  man- 
ganese salt,  so  that  5  mols.  of  oxalate  (670-0)  =  3Mn  (164-79). 

2  Namias  suggests  that  the  zinc  oxide  be  ground  with  sodium  hypochlorite  solution, 
left  for  some  days  and  then  washed  several  times  by  decantation  (Ind.  Chim.  Mm.  e 
Metall.,   1915,  II,  p.  397). 


FERRO-MANGANESE  AND  SPIEGELEISEN  199 

brown,  which  would  indicate  too  large  an  excess  of  the  zinc  oxide)  and  the 
supernatant  liquid  appears  colourless.1  The  precipitate  settles  rapidly  if 
the  flask  is  held  inclined  in  a  suitable  stand. 

When  the  precipitate  has  deposited,  10  c.c.  of  the  permanganate  solu- 
tion are  added,  the  liquid  shaken,  the  precipitate  allowed  to  settle  and,  if 
the  supernatant  liquid  is  colourless,  a  further  10  c.c.  of  permanganate  are 
added,  this  procedure  being  continued  until  the  liquid  contains  excess  of 
the  reagent.  The  excess  of  permanganate  is  titrated  witn  the  sodium 
arsenite  solution,  which  is  added  gradually  and  with  shaking  and  with  an 
interval  after  each  addition  until  the  liquid  is  decolorised.  From  the 
quantity  of  permanganate  used,  less  that  corresponding  with  the  arsenite 
solution  added  (i  c.c.  of  arsenite  =  about  0-5  c.c.  of  permanganate),  the 
amount  of  permanganate  required  to  oxidise  the  manganese  completely 
is  calculated  approximately. 

Titration.  For  the  actual  titration  of  the  manganese,  an  aliquot  part 
of  the  liquid  equal  to  that  used  in  the  preliminary  test  is  oxidised  with 
hydrogen  peroxide,  boiled,  diluted  with  boiling  water  to  600—700  c.c.  and 
zinc  oxide  added  to  precipitate  the  iron. 

While  the  precipitate  is  settling,  the  volume  of  permanganate  found 
necessary  plus  3-4  c.c.  is  introduced  into  a  beaker  and  then  rapidly  poured 
into  the  flask,  the  latter  being  shaken  and  the  beaker  rinsed  out  with  water 
into  the  flask.  When  the  precipitate  has  settled  again,  the  excess  of  per- 
manganate added  is  determined  by  titration  with  the  sodium  arsenite  as 
in  the  preliminary. test.  Next,  in  order  to  determine  the  true  titre  of  the 
arsenite  with  respect  to  the  permanganate  under  the  exact  conditions  used, 
a  further  volume  of  5  c.c.  of  the  permanganate  is  added  and  the  liquid 
again  decolorised  by  the  arsenite  solution.  From  these  data  a  simple 
calculation  gives  the  amount  of  permanganate  required  for  the  complete 
oxidation  of  the  manganese,  and  hence  the  amount  of  the  latter. 

It  is  always  advisable  to  carry  out  control  determinations  on  different 
aliquot  parts  of  the  solution. 

EXAMPLE,  i  c.c.  of  the  permanganate  solution  is  found  to  correspond 
with  0-00165  gram  of  manganese.  In  the  actual  test,  35  c.c.  of  permanganate 
were  added  and  the  excess  required  8  c.c.  of  arsenite  solution,  of  which  9  c.c. 
correspond  with  5  c.c.  of  permanganate.  Since 

9:5=8:  4-44, 

the  amount  of  permanganate  reduced  will  be  35-4-44  =  30-56  c.c.  and  30-56 
.  X  0-00165  =  amount  of  manganese  in  the  aliquot  part  of  the  solution  taken. 

Volhard's  method  is  used  more  especially  in  laboratories  where  estimations 

;pf  manganese  are  made  regularly  ;    it  is  fairly  exact  and,  the  solutions  being 

ready,  fairly  rapid.     It  cannot  be  used  directly  in  presence  of  chromium,  van- 

•adium  and  cobalt,  these  also  reducing  the  permanganate  (for  the  determination 

s'of  manganese  in  presence  of  chromium,  see  p.  185).     Further,  to  steels  contain- 

•ing  large  proportions  of  nickel  the  method  is  not  applicable,  since  the  liquid 

remains  greenish-yellow  and  the  exact  end  of  the  reaction  cannot  be  ascertained 

(for  the  determination  of  manganese  in  presence  of  large  quantities  of  nickel,  see 

p.   1 86).     Many  authors,  instead  of  adding  excess  of  permanganate  and  then 

,-t1  It  is  necessary  to  add  a  slight „ excess  of  zinc  oxide,  but  not  a  large  excess,  which 
may  be  harmful. 


200  FERRO-MANGANESE  AND  SPIEGELEISEN 

titrating  the  excess  with  sodium  arsenite,  prefer  the  simpler  method  of  direct 
titration  :  the  permanganate  solution  is  added  little  by  little  to  the  boiling  liquid 
and  the  precipitate  allowed  to  settle  after  each  addition,  this  being  continued 
until  the  supernatant  liquid  exhibits  a  persistent  pink  colour.  In  this  case,  also, 
a  preliminary  trial  titration  is,  of  course,  necessary.  It  appears,  however,  that 
under  these  conditions,  intermediate  oxides  of  manganese  may  be  formed,  so 
that  the  results  are  not  always  exact. 

(b)  ELECTROLYTIC  DETERMINATION.1 — 1*5  gram  of  the  finely  powdered 
alloy  is  treated,  in  a  covered  porcelain  beaker  of  about  100  c.c.  capacity, 
with  30  c.c.  of  nitric  acid  (D  1-2)  containing  a  few  drops  of  hydrochloric 
acid.  At  the  end  of  the  action,  the  clock-glass  and  the  edges  of  the  beaker 
are  washed  with  water,  1-2  grams  of  ammonium  nitrate  added  and  the 
liquid  evaporated  on  a  water-bath  to  a  syrup  and  then  carefully  over  a 
small  direct  flame  to  redness. 

When  cold,  the  oxides  of  iron  and  manganese  are  dissolved  in  4-5  c.c. 
of  cone,  hydrochloric  acid  in  the  hot,  10  c.c.  of  50%  sulphuric  acid  being 
added  to  the  cooled  liquid  and  the  solution  heated  on  a  sand-bath  until 
the  hydrochloric  acid  is  completely  expelled  and  copious  white  fumes  appear. 
After  being  heated  with  water  to  dissolve  the  sulphates  of  iron  and  man- 
ganese, the  liquid  is  filtered  and  the  filtrate  collected  in  a  250  c.c.  measuring 
flask  and  the  beaker  and  filter  washed  repeatedly  with  boiling  water  acidified 
with  sulphuric  acid. 

The  filter  then  contains  the  silica,  contaminated  by  small  quantities  of 
graphitic  carbon.  If  the  silicon  content  is  required,  the  procedure  given 
on  p.  171  is  followed. 

The  ftquid  in  the  flask  is  made  up  to  250  c.c.  and  50  c.c.  (=  0-3  gram 
of  the  alloy)  z  treated  in  a  100  c.c.  beaker  with  ammonia  until  the  iron 
begins  to  precipitate.  The  liquid  is  then  heated  on  a  steam-bath  and 
dilute  sulphuric  acid  added  drop  by  drop  until  the  ferric  hydroxide  is  com- 
pletely dissolved.  The  solution  of  ferric  and  manganese  sulphates  is  then 
poured  into  a  solution  of  6-7  grams  of  ammonium  oxalate  in  a  little  boiling 
water  contained  in  an  electrolytic  cell  (not  too  narrow),  5-6  c.c.  of  2% 
hydrazine  sulphate  solution  being  added  and  the  liquid  diluted  to  200  c.c. 
and  subjected  to  electrolysis  to  deposit  the  iron  :  ND100  =0-7  amp.,  voltage 
=  4-4-5,  duration  =  3-5  hours,  Winkler  electrodes  (see  later :  Electrolytic 
analysis  of  metals). 

When  the  electrolysis  has  commenced,  2%  hydrazine  sulphate  solution 
is  allowed  to  drop  in  the  neighbourhood  of  the  anode  from  a  small  tap- 
funnel  drawn  out  to  a  capillary  (8-10  drops  per  minute),  this  addition 
being  continued  uninterruptedly  throughout  the  electrolysis. 

As  soon  as  the  liquid  loses  its  yellow  tint  and  becomes  completely  colour- 
less, a  drop  is  removed,  treated  with  a  drop  of  dilute  nitric  acid,  2-3  c.c. 
of  hydrochloric  acid  and  as  much  ammonium  thiocyanate  solution.  When 
only  a  barely  perceptible  pink  coloration  is  thus  obtained,  the  deposition 
of  the  iron  may  be  regarded  as  complete. 

1  Belasio  :    "  Separation  of  Iron  from  Manganese  Electrolytically/*     Ann.  Labor. 
Chim.  Gabelle,   1912,  VI,  p.  207. 

2  With  ferro-manganese  containing  much  manganese,  25  c.c.,    corresponding  with 
0-15  gram  of  the  alloy,  are  taken. 


FERRO-MANGANESE  AND   SPIEGELEISEN  201 

Without  interrupting  the  current,  the  cell  is  then  lowered,  the  electrodes 
being  washed  as  they  emerge  ;  the  cathode  is  next  detached  and,  if  it  is 
to  be  weighed,  washed  further  with  water  and  then  with  alcohol  and  dried 
at  70°. 

The  residual  liquid  is  then  heated — the  anode,  sometimes  covered  with 
manganese  dioxide,  being  kept  immersed — to  destroy  the  ammonium  car- 
bonate formed  by  the  decomposition  of  the  ammonium  oxalate,  to  redissolve 
the  manganese  dioxide,  and  to  reduce  the  volume  to  60-70  c.c.  The  liquid 
is  then  heated  with  1-5  gram  of  chrome  alum  and  10  grams  of  ammonium 
acetate  and  the  hot  solution  filtered  directly  into  the  matte  Classen  capsule. 
After  3  c.c.  of  ammonia  (D  0-94)  have  been  added,  the  liquid  is  mixed, 
brought  to  70-80°  and  subjected  to  electrolysis,  the  capsule  being  con- 
nected with  the  positive  pole.  ND100  =  0-5-0-6  amp.,  voltage  =  2-3, 
temperature  =  70-80°,  duration  =  about  2  hours. 

When  the  deposition  is  found  to  be  complete  by  raising  slightly  the 
level  of  the  liquid,  the  disc  functioning  as  cathode  is  lifted  out  and  the 
contents  of  the  dish  poured  away,  the  deposited  manganese  dioxide  being 
carefully  washed  with  water.  The  dish  is  then  dried  at  100°  and  heated 
at  a  dark-red  heat  to  transform  the  dioxide  and  the  higher  oxides  into  the 
saline  oxide,  Mn3O4. 

When  cold,  the  dish  is  washed  once  more  with  water  to  remove  any 
chromic  acid  which  may  be  included,  again  ignited  and  weighed  rapidly 
to  prevent  the  manganese  oxide  from  absorbing  moisture  :  Mn3O4  X  0-7205 
=  Mn. 

The  electrolytic  method  certainly  takes  longer  than  the  volumetric  method, 
but  has  the  advantage  of  not  requiring  standard  solutions  and  of  being  applicable 
also  in  presence  of  chromium,  cobalt,  nickel  and  vanadium. 

2.  Determination  of  the  Carbon. — This  is  usually  carried  out  by  the 
Corleis  method  (see  Iron,  I,  a)  or,  better,  by  direct  combustion  in  a  current 
of  oxygen  (see  Iron,  i,  b). 

3.  Determination  of  the  Silicon. — When  this  is  required,  it  may  be 
effected  along  with  the  determination  of  the  manganese  (see  Determination 
of  silicon  in  iron,  2,  b). 

4.  Determination   of  the   Phosphorus,   Sulphur   and   Arsenic. — 
These  elements  are  estimated  as  in  cast-  or  wrought-iron. 

*** 

The  manganese  content  of  ferro-manganeses  may  vary  from  25  to  85%  and 
the  carbon  content  from  5  to  7-5%,  the  two  generally  increasing  together. 
Ferro-manganeses  contain  also  0-5-2 -5%  of  silicon,  small  quantities  of  phosphorus 
(0-1-0-4%)  and  minimal  traces  of  sulphur,  copper,  etc. 

Spiegeleisen  contains  0-2-1-2%  of  silicon,  4-5%  of  carbon  and  5-25%  of 
manganese,  and  sometimes,  as  impurities,  small  proportions  of  phosphorus  and 
sulphur. 


202  FERRO-CHROME 

SILICON    FERRO-MANGANESE 

(Silico-spiegeleisen) 

Silicon  ferro-manganese  may  be  regarded  as  a  product  intermediate  to 
ferro-silicon  and  ferro-manganese.  It  is  obtained  in  the  blast  furnace  or 
the  electric  furnace,  the  latter  yielding  especially  pure  products.  Its 
analysis  includes  the  following  : 

1.  Determination    of   the    Silicon. — As    silicon    ferro-manganese    is 
attacked  either  not  at  all  or  with  difficulty  by  acids,  the  silicon  should  be 
estimated  by  the  methods  given  for  the  determination  of  silicon  in  ferro- 
silicon. 

2.  Determination  of  the  Manganese. — As  in  ferro-silicon. 

3.  Determination  of  the  Carbon. — By  direct  combustion  in  a  current 
of  oxygen  (see  Iron,  i,b). 

4.  Determination  of  the  Phosphorus  and  Sulphur. — As  in  ferro- 
silicon. 

* 
*  * 

Silicon  ferro-manganese  obtained  from  the  blast  furnace  contains  about 
20%  Mn,  10-12%  Si  (occasionally  20%),  2-2-5%  C,  0-01-0-2%  P,  and  some- 
times minimal  traces  of  sulphur. 

That  from  the  electric  furnace  may  contain  35-75%  Mn,  20-35%  Si,  0-6-1-5% 
C,  o-oi— 0-06%  P,  0-02—0-03%  S,  and  sometimes  traces  of  copper,  aluminium,  etc. 


FERRO-CHROME 

Ferro-chrome  may  be  prepared  in  the  blast  furnace  or  the  electric 
furnace  and  serves  for  making  chrome  steels.  Its  analysis  includes  : 

1.  Determination  of  the  Chromium. — The  sample  is  best  attacked 
by  the  following  methods.1 

(a)  FUSION  WITH  SODIUM  HYDROXIDE  AND  PEROXIDE.  o-3-o-5  gram  of 
the  very  finely  powdered  sample  are  mixed,  in  a  silver  crucible  or  dish  and 
with  a  silver  spatula,  with  2  grams  of  sodium  hydroxide  in  minute  frag- 
ments, the  mixture  being  covered  with  4  grams  of  sodium  peroxide  and 
heated  to  incipient  fusion,  the  flame  being  then  removed  to  prevent  the 
reaction  from  becoming  too  violent  ;  the  heat  developed  in  the  reaction 
rapidly  melts  all  the  contents  of  the  dish  or  crucible.  A  little  more  sodium 
peroxide  is  added  to  the  fused  mass,  the  latter  being  heated  gradually  to 
fusion  when  the  reaction  begins  to  abate.  After  about  10  minutes,  about 
5  grams  of  sodium  peroxide  are  mixed  in  and  the  mass  heated  rather  more 
energetically  so  as  to  maintain  it  in  a  state  of  quiet  fusion  for  20-30  minutes, 
after  which  a  further  quantity  of  5-6  grams  of  the  peroxide  is  added  and 

1  G.  Gallo  (Rend.  R.  Accademia  Lincei,  1907,  XVI,  p.  58)  proposes  an  ingenious 
method  for  attacking  ferrous  products  with  a  high  content  of  chromium.  It  consists 
in  electrolysing  at  a  temperature  of  80-85°  a  15%  potassium  chloride  solution  rendered 
slightly  alkaline  with  potassium  hydroxide,  using  as  cathode  a  platinum  wire  and  as 
anode  the  metal  to  be  analysed.  All  the  chromium  in  the  latter  is  thus  transformed  into 
alkaline  chromate. 


FERRO-CHROME 


203 


the  heating  then  continued  for  20-30  minutes  longer.  If  finely  powdered, 
the  sample  should  then  be  completely  attacked. 

(b)  FUSION  WITH  SODIUM  CARBONATE  AND  MAGNESIA.  03-0 -5  gram  of 
the  finely  powdered  sample  is  mixed  with  about  10  parts  of  a  mixture 
of  sodium  carbonate  and  magnesium  oxide,  and  the  mixture  heated  in  a 
platinum  crucible  under  the  conditions  prescribed  for  the  analysis  of 
ferro-silicon  (i,  b). 

Titration  of  the  chromium.  The  fused  mass  obtained  by  one  of  the  above 
methods  is  lixiviated  with  water,  as  indicated  on  p.  183  (Chrome  Steels), 
any  manganates  formed  being  reduced  with  sodium  peroxide,  the  liquid 
filtered,  boiled  to  expel  excess  of  sodium  peroxide  and  made  up  to  volume 
in  a  500  c.c.  measuring  flask  ;  the  chromium  is  then  titrated  iodometrically 
on  several  50  or  100  c.c.  portions  (see  Chrome  Steel). 

If  it  is  suspected  that  the  attack  of  the  metal  has  not  been  completed,  the 
residue  from  the  lixiviation  is  dried,  fused  with  sodium  carbonate  and  the  fused 
mass  again  lixiviated,  the  resultant  solution  being  added  to  that  from  the  first 
treatment. 

2.  Determination  of  the  Carbon. — This  is  effected  by  direct  com- 
bustion in  a  current  of  oxygen   (see  Iron,  i,  b}. 

3.  Determination  of  the  Manganese. — The  residue  obtained  in  the 
lixiviation  with  water  of  the  fused  mass  is  dissolved  in  hydrochloric  acid 
and  treated  as  indicated  under  Ferro-silicon,  3. 

4.  Determination  of  the  Silicon,  Phosphorus  and  Sulphur. — As 
in  ferro-silicon. 

*** 

Ferro-chrome  contains  40-65%  Cr  (rarely  80%),  quantities  of  carbon  vary- 
ing according  to  the  degree  of  refining,  and  the  ordinary  impurities  found  in 
cast-iron.  Three  grades  are  distinguished  commercially  : 

1.  Refined  ferro-chrome  No.  i  (0-3-0-75%  C,  60%  Cr). 

2.  Refined  ferro-chrome  No.  2  (1-2%  C,  60%  Cr). 

3.  Ordinary  ferro-chrome  (4-10%  C,  60%  Cr). 

The  following  table  gives  the  mean  compositions  of  various  ferro-chromes 
(Bonini)  : 

TABLE   XVI 
Composition  of  Ferro-chromes 


Type. 

Cr 

Fe 

C 

Si 

Al 

Mn 

Ca 

S 

P 

8-10%  of  carbon 

54-50 

22-00 

9-50 

2-25 

0-80 

0-15 

0-25 

0-04 

0-03 

7-8% 

63-50 

21-50 

7-50 

5-30 

0-80 

0-16 

0-25 

0-04 

0-03 

5-6% 

64-00 

28-50 

5-50 

0-40 

0-50 

0-15 

0-25 

0-04 

O-O2 

3-4% 

64-00 

31-oc 

3-50 

0-40 

0-40 

0-15 

0-30 

0-04 

0-02 

Less  than  i  %  of  carboi 

63-50 

35-oc 

^.-60 

0-20 

o-ic 

o-io 

o-35 

^•03 

O-O2 

204  FERRO-TUNGSTEN 


FERRO -TUNGSTEN 

Ferro-tungsten  is  obtained  by  the  direct  reduction  of  natural  wolframite 
or  scheelite  with  carbon  in  a  crucible,  or  in  the  blast  furnace  or  the  electric 
furnace,  and  serves  for  the  preparation  of  tungsten  steels. 

Ferro-tungsten  and  steels  with  high  tungsten  contents  (20%)  are  in- 
soluble or  difficultly  soluble  in  acids,  and  to  attack  them  it  is  necessary  to 
fuse  with  alkali.  Their  analysis  includes  : 

1.  Determination  of  the  Tungsten. — 0-5-2  grams  of  the  finely  pow- 
dered sample  are  fused  with  10  parts  of  the  mixture  of  sodium  carbonate 
and  magnesia,  as  under  Ferro-silicon,  i  b,  or  i  gram  of  the  sample  may  be 
fused  with  4—5  grams  of  sodium-potassium  carbonate  and  0-5  gram  of 
potassium  nitrate.     In  either  case,  the  product  is  lixiviated  with  hot  water, 
sodium  peroxide  being  added  and  the  liquid  boiled  to  destroy  the  excess 
of  this  reagent,  if  the  solution  appears  greenish  owing  to  the  presence  of 
manganates.     The  liquid,  which  contains  the  tungsten  as  sodium  tungstate, 
is  filtered  into  a  500  c.c.  measuring  flask  and  the  residue  repeatedly  washed, 
dried  and  again  fused  with  sodium  carbonate,  the  mass  being  lixiviated  to 
recover  any  small  amount  of  tungsten  which  may  have  resisted  the  first 
attack. 

An  aliquot  part  (50  or  100  c.c.)  of  the  total  solution  is  acidified  with 
hydrochloric  acid,  evaporated  to  dryness,  heated  at  135°,  taken  up  again 
in  hydrochloric  acid,  etc.,  as  described  for  the  analysis  of  tungsten  steel. 

2.  Determination  of  the  Carbon. — With  products  insoluble  in  acid, 
direct  oxidation  in  a  current  of  oxygen  must  be  employed  (see  Iron,  i,  b). 

3.  Determination   of  the    Silicon. — The  procedure   employed   with 
ferro-silicon  is  followed,  but  since  tungstic  acid  separates  with  the  silica, 
the  latter  is  treated  with  hydrofluoric  acid  and  estimated  by  the  loss  in 
weight  (see  Tungsten  Steels). 

4.  Determination  of  the  Manganese. — This  is  carried  out  on  the 
residue  remaining  undissolved  when  the  fused  mass  is  lixiviated  with  water 
(see  Ferro-silicon,  3). 

5.  Determination  of  the  Phosphorus  and  Sulphur. — As  in  ferro- 
silicon  (see  p.  196). 

*** 

Crucible  ferro-tungsten  contains,  on  the  average,  25-30%  W,  60-70%  Fe 
1-1 '5%  C>  with  traces  of  manganese,  phosphorus,  etc.  ;  that  from  the  blast 
furnace  always  contains  considerable  proportions  of  manganese  (in  some  types, 
up  to  40%)  and  carbon  (4-5%). 

Ferro-tungsten  obtained  in  the  electric  furnace  usually  has  a  high  tungsten 
content  (80-90%  W,  10-20%  Fe,  very  small  amounts  of  carbon,  silicon  and 
manganese).  Sometimes  small  quantities  of  calcium,  magnesium,  titanium, 
aluminium,  nickel,  molybdenum,  vanadium,  etc.,  are  also  found. 

The  mean  percentage  compositions  of  some  of  the  ferro-tungstens  prepared 
in  the  electric  furnace  are  as  follows  (Bonini)  : 


FERRO- VANADIUM 


205 


TABLE   XVII 
Composition  of  Ferro- tungstens 


No. 

W 

Fe 

C 

Si 

Mn 

Al 

Sn 

s 

p 

I 

72-5 

23-29 

i-75 

o-33 

0-80 

0-06 

O-OI 

o-oi 

2 

64-7 

— 

1-36 

o-33 

o-43 

0-09 

Trace 

o-oi 

0-007 

3 

87-4 

— 

0-38 

0-13 

— 

— 

Trace 

0-07 

0-009 

4 

70-75 

22-O 

— 

0-3 

0-8 

— 

— 

O-OI 

O-O2 

5 

83-3 

I5-72 

0-52 

0-13 

' 

—  ~ 

o-oi 

o-oi 

FERRO  -VANADIUM 

Ferro-vanadium  is  obtained  exclusively  by  electro-thermal  processes, 
or  by  these  in  combination  with  alumino-thermal  processes,  from  mixtures 
of  ferric  oxide  and  vanadium  oxide.  They  serve  as  deoxidising  agents 
in  the  refining  of  cast-iron  and  steels,  and  for  the  preparation  of  vanadium 
steels. 

As  prepared  to-day  it  is  comparatively  pure  and,  besides  iron  and  vana- 
dium, usually  contains  only  small  quantities  of  carbon  and  silicon  and  some- 
times traces  of  phosphorus  and  manganese.  Its  analysis  includes  : 

1.  Determination  of  the  Vanadium.  —  -1-2  grams  of  the  sample  are 
treated  in  a  small  porcelain  dish  with  nitric  acid  (D  1-18),  evaporated  to 
dryness,  calcined  and  the  oxides  obtained  fused  with  sodium  peroxide, 
the  product  being  extracted  with  water  as  indicated  in  the  analysis  of 
vanadium  steels.1 

The  liquids  from  the  lixiviation  are  together  made  up  to  500  c.c.  and 
the  vanadium  in  an  aliquot  part  determined  as  with  vanadium  steel. 

2.  Determination  of  the  Carbon  and  Silicon.  —  As  in  ordinary  cast- 
iron. 

3.  Determination  of  the  Phosphorus.  —  This  is  carried  out  on  an 
aliquot  part  of  the  500  c.c.  (see  i,  above)  by  the  method  given  for  estimating 
phosphorus  in  presence  of  vanadium  (see  Iron,  4,  3). 

4.  Determination  of  the  Manganese.  —  As  in  ferro-silicon. 


The  usual  types  of  ferro-vanadium  contain  35-55%  of  vanadium,  with 
small  quantities  of  silicon  (0-09-1-2%)  and  carbon  (1-3%)  and  traces  of  phos- 
phorus, sulphur,  magnesium  and  aluminium. 

The  mean  compositions  of  ferro-vanadiums  made  in  the  electric  furnace  are 
as  follows  (Bonini)  : 

1  If  the  sample  can  be  finely  powdered,  it  may  be  fused  at  once  with  a  mixture  of 
sodium  carbonate  and  magnesia  (see  p.  195),  the  mass  obtained  being  lixiviated  with 
water. 


206 


FERRO-MOLYBDENUM 


TABLE   XVIII 
Compositions  of  Ferro- vanadium 


No. 

V 

Fe 

C 

Si 

Al 

Mn 

Cu 

s 

p 

I 

55-o 

40-00 

4-00 

0-30 

O-IO 

0-30 



0-03 

0-04 

2 

52-8 

45-84 

1-04 

0-09 



— 

— 

0-025 

O-O2 

3 

47'4 

51-20 

1-07 

O-O9 



0-07 

o-oi 

0-009 



4 

34'i 

64-22 

1-42 

O-I2 

O-I2 

0-12 



0-03 

O-OO9 

FERRO  -MOLYBDENUM 

This  is  obtained  industrially  by  electro-thermal  processes  and  is  used 
essentially,  together  with  chromo-molybdenum  and  molybdenum,  for 
making  molybdenum  steels.  The  elements  commonly  estimated  are 
molybdenum,  carbon,  silicon,  manganese,  phosphorus,  sulphur  and  tungsten. 

1.  Determination  of  the   Molybdenum.— 1-2   grams  of  the  finely 
powdered  sample  are  heated  at  not  too  high  a  temperature  with  about  10 
parts  of  the  sodium  carbonate  and  magnesia  mixture,  the  semi-fused  mass 
being  extracted  with  hot  water  ;    these  operations  are  then  repeated  to 
extract  any  small  quantities  of  molybdenum  remaining  in  the  residue  (see 
Chrome  Steels).     The  two  solutions  together  are  made  up  to  500  c.c.  in  a 
measuring  flask  and  the  molybdenum  in  an  aliquot  part  (50—100  c.c.) 
determined  as  in  molybdenum  steels. 

2.  Determination  of  the  Carbon. — By  direct  combustion  in  a  current 
of  oxygen  (see  Iron,  i,  b). 

3.  Determination   of  the   Silicon,   Manganese,   Phosphorus   and 
Sulphur. — As  in  ferro-silicon. 

4.  Determination  of  the  Tungsten.— In  an  aliquot  part  of  the  500 
c.c.  of  solution  (see  I,  above)  the  tungsten  is  determined  as  in  ferro-tungsten. 

*** 

According  to  the  character  of  the  original  ores,  different  types  of  ferro- 
molybdenum  are  obtained.  These  may  contain  15-80%  of  molybdenum 
(usually  50-70%),  from  0-5%  (for  the  more  refined  products)  to  5%  of  carbon, 
0-1-0-5%  of  silicon  and  small  quantities  of  manganese,  sulphur,  phosphorus, 
and  sometimes  tungsten. 

The  commoner  commercial  products  have  the  following  mean  compositions 
(Guillet)  : 

TABLE   XIX 
Compositions  of  Ferro -molybdenum 


Type. 

Mo 

C 

Fe 

Si 

Al 

S 

P 

Ordinary  ferro  -molybdenum 

53-30 

I-87 

_ 

0-17 

Trace 

0-03 

0-03 

Refined 

52-00 

0'34 

— 

0-09 

— 

o-oi 

0-OO9 

Rich 

84-80 

2-27 

— 

o-ii 

— 

O'O2 

O-OO7 

FERRO-TITANIUM  207 

FERRO -TITANIUM 

Ferro-titanium  is  prepared  by  electro-thermal  and  alumino-thermal 
processes  from  rutile  and  from  iron  ores  rich  in  titanium,  and  serves  as  a 
deoxidising  agent  in  the  refining  of  cast-iron  and  steel. 

1 .  Determination  of  the  Titanium.1 — 0-5  gram  of  the  finely  powdered 
sample  is  heated  in  a  platinum  crucible  and,  after  cooling,  evaporated  to 
dryness  with  a  few  c.c.  of  hydrofluoric  acid.     The  residue  is  then  heated 
for  a  short  time  in  the  same  crucible  with  5-7  grams  of  potassium  bisulphate, 
the  cooled  mass  taken  up  in  hydrochloric  acid  (not  too  dilute)  and  heated 
on  the  water-bath  until  solution  is  complete.     The  liquid  is  made  up  to 
500-600  c.c.,  mixed  with  20-30  c.c.   of  concentrated  sodium  bisulphite 
solution  and  heated  gently  to  reduce  the  iron  to  ferrous  salts  (a  drop  of 
the  solution  should  give  no  appreciable  colour  with  thiocyanate).     When 
the  reduction  is  complete  and  the  temperature  of  the  liquid  not  above 
about  40°,  an  addition  is  made,  in  one  quantity  and  with  shaking,  of  70- 
100  c.c.  of  concentrated  ammonia  containing  in  solution  30  grams  of  potas- 
sium cyanide.     The  solution  is  then  heated  rapidly  and  kept  near  to  the 
boiling  point  until  the  precipitate  appears  white  and  the  supernatant  liquid 
has  assumed  a  greenish-yellow  coloration.     When  cold,  the  liquid  is  filtered 
and  the  precipitate  washed,   first  with  ammoniacal  ammonium  sulphite 
solution  and  then  with  hot  water.     The  moist  precipitate  is  dissolved  in 
hot,  dilute  hydrochloric  acid  and  the  titanium  oxide  in  the  clear  solution 
precipitated  by  fresh  addition  of  ammonia.     The  precipitate  is  filtered, 
washed,  ignited  strongly  and  weighed  :    TiO2  X  0-6005  —  Ti. 

When  aluminium  occurs  along  with  the  titanium,  the  oxides  thus 
separated  are  fused  with  bisulphate,  the  fused  mass  dissolved  in  hydro- 
chloric acid  and  the  titanium  separated  from  the  aluminium  by  means  of 
cupferron.2 

2.  Determination  of  the  Carbon. — By  direct  combustion  in  a  current 
of  oxygen'3  (see  Iron,  I,  6). 

3.  Determination   of  the  Silicon/ — 0-3-1   gram  is  disintegrated  with 
the  mixture  of  sodium  carbonate  and  magnesia  (see   Ferro-silicon,  i,  b,  p. 
195).     When  cold,  the  semi-fused  mass  is  moistened  with  water,  ground 
in  a  mortar  and  poured  into  a  beaker,  the  least  possible  quantity  of  rinsing 
water  being  used.     The  liquid  is  strongly  acidified  with  hydrochloric  acid 
— heating  being  avoided — left  for  1-2  hours  and  then  heated  on  a  water- 
bath  until  the  liquid  becomes  perfectly  clear.     The  solution  is  evaporated 
in  presence  of  sulphuric  acid,  heated  until  copious  white  fumes  appear, 
diluted  when  cold  and  the  separated  silicon  filtered  off  (see  Ferro-silicon,  i,  b). 

4.  Determination  of  the  Manganese,  Phosphorus  and  Sulphur. — 
As  in  ferro-silicon. 


*  * 


1  Von  Woldemar  Trautmann  (Zeitschr.  ang.  Chem.,  1911,  p.  877  ;    Boernemann  and 
Schirrmeister  (Zeitschr.  ang.  Chem.,   1911,  p.  709). 

2  Bellucci  and  Grass!  :    Gazz.  Chim.  Ital.,   1913,  i,  p.  570. 

3  With  products  very  rich  in  silica,  disintegration  in  a  current  of  chlorine  must  be 
employed, 


208 


FERRO- ALUMINIUM 


In  small  quantities  (0-2%)  titanium  is  often  found  in  ordinary    cast-iron. 
The  compositions  of  some  of  the  commoner  ferro -titaniums  are  as  follows  : 

TABLE   XX 
Composition  of  Ferro -titanium 


No. 

Fe 

Ti 

c 

Si 

Al 

Mn 

S 

P 

I 

36-85 

56-63 

4-62 

1-25 

0-44 

o-io 

0-045 

O-O2 

2 

78-54 

18-37 

0-67 

1-40 

0-69 

0-18 

0-074 

0-O24 

3 

87-68 

11-21 

0-67 

o-37 

~ 

~ 

0-03 

0-04 

FERRO  -ALUMINIUM 

Ferro- aluminium  is  usually  prepared  in  the  electric  furnace  by  reducing 
alumina  in  presence  of  iron,  and  serves,  like  metallic  aluminium — which 
is  much  more  used  at  the  present  time — -as  a  deoxidising  agent  in  the  refining 
of  cast-iron  and  steel.  Its  analysis  includes  : 

1.  Determination  of  the  Aluminium. — Exact  determination  of  the 
aluminium  necessitates  preliminary  expulsion  of  the  iron  by  exhaustion 
with  ether  in  Rothe's  apparatus,  the  aluminium  being  then  precipitated  as 
phosphate.1  When,  however,  very  exact  determination  is  not  required, 
the  following  more  rapid  method  (Regelsberger's)  may  be  followed. 

5  grams  of  the  coarsely  powdered  sample  are  dissolved  in  a  porcelain 
dish  in  dilute  sulphuric  acid  (i  14),  evaporated  to  dryness  and  heated  on 
a  sand-bath  until  white  fumes  are  emitted.  When  cold  the  sulphates  are 
dissolved  in  hot  water  and  the  solution  poured  into  a  300  c.c.  measuring 
flask,  cooled,  made  up  to  volume,  and  filtered  through  a  dry  pleated  filter 
into  a  dry  vessel. 

To  100  c.c.  of  the  filtrate  sodium  bisulphite  or  hyposulphite  is  added 
until  the  iron  is  completely  reduced  (a  drop  of  the  liquid  should  give  no 
colour  with  thiocyanate),  the  liquid  cooled,  most  of  the  free  acid  neutralised 
with  sodium  carbonate,  and  the  solution  poured  into  a  boiling  mixture 
of  50  c.c.  of  sodium  hydroxide  solution  (containing  10  grams  of  sodium 
hydroxide)  with  40  c.c.  of  potassium  cyanide  solution  (containing  8  grams 
of  potassium  cyanide).2  When  cold,  the  liquid  is  introduced  into  a  500 
c.c.  measuring  flask,  made  up  to  volume,  and  filtered  through  a  dry  filter. 
To  300  c.c.  of  the  filtrate  (=  I  gram  of  the  alloy),  concentrated  ammonium 
nitrate  solution  (15  grams  in  a  little  water)  is  added,  the  liquid  being  boiled 
to  expel  most  of  the  ammonia,  and  the  precipitated  aluminium  hydroxide 
filtered  off,  washed  until  the  washing  water  no  longer  gives  a  blue  coloration 
with  ferric  chloride,  dried,  ignited  and  weighed  :  A12O3  X  0-5303  =  Al. 

If  the  ammoniacal  solution  is  heated  too  long,  a  little  ferric  hydroxide 
may  be  precipitated  with  the  aluminium.  In  this  case,  the  calcined  and 

1  See  A.  Ledebur  :    Leitfaden  fur  Eisenhutten  Labor atorien,  gth  edition,  p.  153. 

2  If  the  reduction  were  not  complete,  small  quantities  of  iron  and  manganese  might 
be  precipitated  as  hydroxides. 


ELECTROLYTIC  ANALYSIS   OF  METALS 


209 


weighed  alumina  is  finely  powdered  and  treated  with  hydrochloric  acid 
until  it  appears  white,  the  iron  reduced,  without  nitration,  by  means  of 
zinc  amalgam,  and  titrated  with  permanganate  ;  the  corresponding  amount 
of  ferric  oxide  is  deducted  from  the  total  weight  of  the  alumina. 

2.  Determination  of  the  Carbon,  Silicon,  Manganese,  Phosphorus 
and  Sulphur. — As  with  iron  (see  p.  163). 

The  more  usual  types  of  ferro-aluminium  contain  10-20%  of  aluminium. 

ELECTROLYTIC   ANALYSIS    OF   METALS 

Analysis  by  the  electrolytic  method  has  now  reached  a  high  degree  o 
perfection  and  forms  a  valuable  aid  in  the  examination  of  metals  and  alloys 
Owing  to  their  accuracy,  their  simplicity  and  their  neatness,  electrolytic 
methods  will  be  given  the  preference  over  other  methods,  and  a  brief  descrip- 
tion of  the  necessary  apparatus  and  a  short  outline  of  the  conditions  to  be 
observed  in  the  various  operations  will  now  be  given. 

1.  Sources  of  Current. — The  continuous  current  used  should  not  be 
very  intense  but  must  be  as  far  as  possible  constant.  It  may  be  obtained 
from  :  primary  batteries,  accumulators,  or  the  street  mains. 

Primary  batteries  do  not  answer  very  well  the  requirements  of  elec- 


FIG.  1 6 


trolytic  analysis,  since  they  usually  yield  a  feeble  current  and  must  there- 
fore consist  of  numerous  cells,  while  they  discharge  rapidly  and  are  there- 
fore costly.  The  most  suitable,  owing  to  the  constancy  of  the  current 
produced,  are  :  the  Daniell  cell  and  its  modifications,  and  the  Cupron  cell. 
Also  thermo-electric  piles,  although  very  delicate,  may  be  usefully  employed. 
Accumulators  are,  however,  very  satisfactory,  as  regards  both  con- 
stancy of  current  and  capacity,  and  they  should  be  used  in  all  plants  of  good 

A.C.  H 


210 


ELECTROLYTIC  ANALYSIS  OF  METALS 


O-O--TO 


FIG.  17 


size.  For  analysis  with  stationary  electrodes,  a  battery  of  4  elements  of 
30-50  ampere-hour  capacity  is  sufficient,  whilst  rotating  electrodes  may 
require  12  accumulators  of  this  capacity.  The  various  elements  should 
connect  with  either  a  mercury  or  plug  commutator,  so  that  they  may  be 
grouped  readily  in  parallel  or  in  series  or  in  mixed  formation  according  to 
circumstances. 

The  electricity  supply  current  may  also  be  used  and,  if  continuous,  requires 

only  the  insertion  of  suitable  resist- 
ances. If  alternating,  it  must  be  con- 
verted into  continuous  current  by  an 
electrolytic  rectifier,  which  serves  par- 
ticularly well  when  only  low  current 
intensities  are  required  (i^i'S  amp.). 

Fig.  1 6  shows  an  electrolytic  rec- 
tifier in  connection  with  a  small 
switchboard  and  the  other  arrange- 
ments necessary  for  electrolytic 
analysis. 

2.  Distribution  of  the  Current. 
—The  switchboard  for  distributing 
the  current  is  very  simple.  It  includes 
essentially  a  rheostat  (Fig.  17,  R)  to 

regulate  the  current,  an  accurate  amperemeter  and  voltmeter,  a  commu- 
tator C  for  inserting  or  cutting-out  the  amperemeter  in  the  circuit  including 
the  electrolytic  cell,  and  an  interrupter  B  to  insert  at  will  the  voltmeter 
and  measure  the  pressure  at  the  terminals.  In  any  laboratory  the  current 
may  be  distributed  in  the  form  most  convenient  to  the  particular  circum- 
stances. 

3.  Electrodes  and  Supports. — In  general  the  electrodes  are  of  plati- 
num or  iridised  platinum  and 
that  on  which  the  metal  is  de- 
posited, that  is,  the  cathode,  is 
of  greater  surface  than  the 
anode. 

(a)  WITH  STATIONARY  ELEC- 
TRODES. Electrodes.  Of  the 
numerous  electrodes  of  different 
form  and  dimensions  which  have 
been  suggested,  those  most  suit- 
able in  practice  are  : 

The  Classen  dish,  with  a 
smooth  or  matte  surface  (Fig.  18,  a).  This  is  a  platinum  dish  of  slightly 
convex  base,  weighing  about  40  grams,  holding  about  200  c.c.  and  con- 
stituting the  cathode.  The  anode  is  a  disc  of  about  4-5  cm.  in  diameter 
with  5  holes,  and  supported  by  a  stout  platinum  wire  (Fig.  18,  c)  ', 
instead  of  this,  a  horizontal  wire  spiral  may  be  used  (Fig.  18,  b). 

Winkler's  gauze  electrodes.     These  are  generally  preferred  because  they 
weigh  little  (14-15  grams),  permit  perfect  mixing  of  the  liquid,  are  readily 


FIG.  i 8. 


ELECTROLYTIC  ANALYSIS   OF  METALS 


211 


'-:l 


FIG.  19 


washed  and,  what  is  of  great  practical  importance,  allow  of  the  electrolysis 
of  solutions  varying  in  volume  from  100  to  300-400  c.c.  and  of  electrolysis 
in  presence  of  precipitates.  The  cathode  consists  of  an  open  cylinder  5  cm. 
high  and  3-5  cm.  in  diameter,  formed  of  iridised 
platinum  gauze  and  supported  by  a  thick  plati- 
num wire  (Fig.  19,  a).  The  anode  forms  a  plati- 
num wire  spiral  (Fig.  19,  b). 

In  many  cases,  especially  when  copper  and 
lead  are  being  determined  simultaneously,  the 
Winkler  spiral  may  be  replaced  with  advantage 
by  a  small  cylinder  of  iridised,  matte  platinum 
gauze,1  1-5  cm.  in  diameter  and  5  cm.  high  (Fig. 
19,  c)  ;  on  this  as  much  as  0-3  gram  of  lead  may 
be  conveniently  deposited  as  peroxide,  whilst 
the  copper  is  deposited  on  the  cathode. 

Supports.  The  most  convenient  and  the 
most  common  are  those  of  Classen.  They  con- 
sist of  a  heavy  iron  foot  carrying  a  thick  vertical 
glass  rod.  To  the  insulating  rod  are  fixed  by 
means  of  pressure  screws,  the  electrode  holders, 
those  for  Classen  electrodes  being  a  ring  furnished  with  three  platinum 
points  on  which  the  dish  rests  and  a  binding  screw  for  suspending  the 
anode,  and  those  for  Winkler  electrodes  two  connecting  screws  (see  Fig. 

16). 

(b}  WITH  ROTATING  ELEC- 
TRODES. Electrodes.  These  may 
be  :  the  Classen  dish,  within  which 
the  disc  acting  as  anode  revolves  ; 
or  the  Winkler  cathode,  inside 
which  rotates  a  platinum  spiral 
wound  round  a  glass  rod  to  give  it 
solidity  (Fig.  21).  Other  electrodes 
which  are  much  in  use  and  very 
convenient  are  those  of  Fischer, 
consisting  of  two  concentric  gauze 
cylinders  (Fig.  20,  a,  b),  insulated 
by  quartz  rods  ;  the  electrodes  re- 
main stationary,  the  liquid  being 
kept  in  motion  by  a  glass  stirrer 
(Fig.  20,  c)  revolving  inside  the 
smaller  cylinder. 
FIG.  20  Stands.  These,  besides  supporting 

the  electrodes,  should  permit  of  the 

rotation  of  one  of  the  electrodes  or  of  a  stirrer.  In  its  simplest  form,  a 
stand  for  rotating  electrodes  is  shown  in  Fig.  21.  One  of  the  screws  of 
the  stand  is  replaced  by  a  support  carrying  a. rotating  axis  on  which  the 

1  Belasio  :   "Analysis  of  Bronzes  for  Ornamentation,  so-called  Nickel  Bronzes"  (Ras- 
segna  mineraria,   1909,  XXXI,  p.  50). 


212 


ELECTROLYTIC  ANALYSIS  OF  METALS 


anode  is  fixed.  The  rotation  may  be  imparted  by  a  water  turbine  or  an 
electric  motor  of  adjustable  speed.  Much  more  perfect  is  the  Fischer 
stand  made  for  his  electrodes  and  suitable  also  for  use  with  the  Classen 
dish  (Fig.  22). 

Another  means  for  obtaining  the  rotation  of  the  electrolyte  is  that  pro- 


O 
FIG.  21. 


JLL 


FlG.    22. 


posed  by  Frary  and  based  on  the  principle  that  any  conductor  carrying 
a  current  and  situate  in  a  magnetic  field  tends  to  move  with  a  velocity 
depending  on  the  intensities  of  the  current  and  of  the  magnetic  field.  The 
arrangement  of  the  apparatus  is  shown  in  Fig.  23.  In  practice,  preference 

is  given  to  mechanical  methods  of  agitation. 
Practical  Rules. — When  use  is  made  of 
Winkler's  electrodes,    which    are    the    most 
practical,  the  electrolysis  is  carried  out   in   a 
K     beaker  which  is  fairly  tall  and  not  too  narrow. 
-     The   prescribed  reagents  are  added,  suitably 
diluted  so  that  the  electrodes    remain  com- 
pletely immersed,  and  mixed.     The  beaker  is 
placed  on  a  stand  of  adjustable  height  or  on 
a   tripod   fitted  with  wire  gauze  if  the  elec- 
trolysis is  to  be  carried  out  in  the  hot.     The 
electrodes  are  then  arranged,  care  being  taken 
that  the  bottom  of  the  cathode  is  about   i 
FIG.  23  cm.  from  the  bottom  of  the  beaker  and  that 

the  anode  is  exactly  in  the  middle  of  the  gauze 

cylinder  and  almost  touches  the  base  of  the  beaker.  The  latter  is  then 
covered  with  a  divided  clock-glass  with  three  semicircular  gaps  in  each 
.half,  so  that  three  circular  holes  are  left  to  take  the  stems  of  the 


ELECTROLYTIC  ANALYSIS  OF  METALS  213 

electrodes  and  a  thermometer,  if  this  is  required.  The  handle  of  the 
rheostat  is  placed  to  give  the  maximum  resistance,  the  current  started, 
the  amperemeter  and  voltmeter  inserted  in  the  circuit,  and  the  rheostat 
gradually  regulated  until  the  measuring  instruments  indicate  the  proper 
current  and  voltage  ;  the  instruments  are  then  cut  out. 

With  the  Classen  capsule  the  same  directions  are  to  be  followed.  The 
dish  containing  the  electrolyte  is  placed  on  the  proper  stand,  the  anode 
arranged  centrally  and  a  few  centimetres  from  the  bottom,  the  cover  fitted 
and  so  on,  as  above. 

When  rotating  electrodes  are  used,  the  procedure  is  the  same  :  when 
the  electrodes  are  in  place,  the  rotating  apparatus  is  started  so  as  to  give 
the  prescribed  velocity  (number  of  turns  per  minute),  the  cover  fitted,  the 
current  regulated  and  the  electrolysis  continued. 

Detection  of  the  End  of  the  Deposition. — When  the  prescribed  time 
has  elapsed,  the  deposition  of  the  metal  to  be  determined  should  be  com- 
plete. To  ascertain  if  this  is  so,  two  means  are  used  :  (i)  If  the  deposited 
metal  is  different  in  colour  from  platinum  (e.g.,  copper),  the  level  of  the 
electrolyte  is  raised  a  few  millimetres  by  addition  of  water ;  if,  after  some 
time  (15  minutes),  the  newly  immersed  part  of  the  electrode  shows  no 
coating  of  the  metal  being  determined,  the  deposition  is  complete.  (2)  A 
drop  of  the  electrolyte  is  removed  and  tested  for  the  metal  by  its  most 
sensitive  reactions. 

Washing  of  the  Electrodes. — With  Winkler  electrodes,  the  washing 
is  very  simple.  The  covers  and  thermometer  are  removed  and  washed 
with  water,  the  beaker  grasped  in  the  left  hand  and  the  supporting  stand 
removed  without  interrupting  the  current.  The  beaker  is  then  rapidly 
but  carefully  lowered  and  replaced  by  a  small  beaker,  which  contains, 
according  to  circumstances,  distilled  water  or  water  acidified  with  sulphuric 
acid  and  is  supported  on  the  stand.  After  10-15  minutes  the  cathode  is 
detached,  washed  by  a  gentle  jet  of  distilled  water,  then  with  alcohol  and 
finally  with  ether,  dried  in  an  oven  at  60-70°,  cooled  in  a  desiccator  and 
weighed. 

With  the  Classen  dish  two  cases  present  themselves.  If  the  electrolyte 
has  no  energetic  solvent  action  on  the  deposited  metal,  the  covers  are 
removed,  the  anode  detached  and  placed  in  a  beaker  which  is  kept  near, 
the  dish  being  emptied  into  the  same  beaker  and  washed  with  a  little  water. 
The  washing  is  then  completed  with  water,  alcohol  and  ether,  and  the  dish 
dried  at  60-70°,  cooled  in  a  desiccator  and  weighed.  If,  however,  the 
electrolyte  is  acid,  it  may  attack  the  metallic  deposit  during  these  manipu- 
lations ;  in  this  case,  the  washing  should  be  carried  out  without  interrupting 
the  current.  A  small  stream  of  distilled  water  is  passed  into  the  dish  by 
means  of  a  Marriotte's  bottle  or  otherwise,  while  at  the  same  time  the  liquid 
is  drawn  off,  by  a  syphon  reaching  almost  to  the  bottom  of  the  dish,  at 
such  a  rate  that  the  level  of  the  surface  is  always  slightly  above  the  deposited 
metal.  This  process  is  continued  until  the  solution  in  the  dish  assumes  a 
neutral  reaction.  The  dish  is  then  removed  from  its  stand,  washed  with 
water,  alcohol  and  ether,  and  dried  at  60-70°. 

With  rotating  electrodes,  the  same  precautions  are  followed  :    at  the 


214  COPPER  AND   ITS  ALLOYS 

end  of  the  electrolysis  the  current  is  lowered,  the  rotation  stopped  and  the 
usual  washing  and  drying  of  the  cathode  effected. 

Dissolution  of  the  Metallic  Deposits. — Deposits  of  copper,  zinc, 
nickel,  silver,  etc.,  are  dissolved  in  nitric  acid  ;  tin  and  iron  in  hydrochloric 
acid  ;  antimony  in  nitric  acid  containing  a  little  tartaric  acid  in  solution  ; 
lead  peroxide  in  nitric  acid  with  a  little  oxalic  acid  dissolved  in  it  ;  man- 
ganous-manganic  oxide  in  dilute  sulphuric  acid  containing  hydrogen  peroxide. 
When  Winkler  electrodes  are  used,  it  is  very  convenient  to  immerse  them 
in  a  tall,  narrow  vessel  fitted  with  a  ground  stopper  and  containing  the 
proper  acid,  which  may  be  used  repeatedly. 


COPPER   AND    ITS   ALLOYS 

The  more  important  commercial  products  are  :  refined  and  electrolytic 
copper  and  its  various  alloys  with  phosphorus,  silicon,  manganese,  zinc, 
tin  and  nickel. 

After  the  usual  tests  for  industrial  copper,  methods  for  the  analysis  of 
its  principal  alloys  will  be  given,  beginning  with  alloys  of  copper  with  phos- 
phorus, silicon  and  manganese,  and  coming  later  to  the  most  important 
ones,  namely,  the  ordinary  and  special  brasses  and  the  ordinary  and  special 
bronzes. 

Alloys  of  copper  with  nickel  and  zinc  (argentan)  will  be  treated  along 
with  nickel  and  its  alloys,  and  its  alloys  with  tin  and  antimony  (anti-friction 
metals)  along  with  tin  and  its  alloys. 

COPPER 

The  complete  analysis  of  commercial  copper,  that  is,  the  determination 
of  the  copper  and  of  all  the  extraneous  elements  accompanying  it  in  large 
or  small  proportions  (Bi,  Pb,  Sb,  As,  Sn,  Ag,  Au,  Fe,  Ni,  Co,  Zn,  S,  Se, 
Te,  C,  P,  Si,  O,  etc.)  is  a  very  long  and  delicate  operation.1  Beyond  a 
determination  of  the  copper,  commercial  analyses  as  a  rule  require  only 
estimations  of  the  more  injurious  elements,  especially  of  bismuth,  arsenic, 
phosphorus,  antimony,  lead,  sulphur,  nickel,  iron  and  oxygen.  Rapid 
and  exact  methods  for  determining  these  elements  will,  therefore,  be  given. 

1.  Determination  of  the  Copper  (by  electrolysis}. — 5  grams  of 
the  metal  in  fine  turnings,  freed  from  fat  by  means  of  ether  and  from  traces 
of  iron  from  the  sampling  tool  by  means  of  a  magnet,  are  placed  in  a  tall, 
narrow  beaker  covered  with  a  clock-glass  or  with  an  inverted  funnel  of 
rather  less  diameter  than  the  mouth  of  the  beaker.  The  metal  is  there 
covered  with  water  and  treated  with  5-7  c.c.  of  cone,  sulphuric  acid  and 
15-20  c.c.  of  nitric  acid  (D  1-33),  gentle  heat  being  applied  towards  the 
end  of  the  action.  Refined  copper  usually  dissolves,  but  unrefined  metal 
may  leave  a  residue  and  traces  of  copper  occluded  in  the  latter  must  be 
extracted  by  boiling.  In  either  case  the  unfiltered  liquid  is  made  up  to 

1  See  Hampe  :  Chem.  Zeit.,  1893,  XVII,  p.  1678  ;  Fresenius  :  Quantitative  Analysis  ; 
A.  Hollard  :  Chem.  Zeit.,  1900,  XXIV,  p.  146. 


COPPER  215 

250-300  c.c.  and  electrolysed  at  the  ordinary  temperature  with  a  current 
of  0-5-1  amp.,  using  Winkler  electrodes  ;    duration,  12-15  hours. 

When  the  deposition  is  complete  (see  p.  213),  the  electrolytic  beaker 
is  replaced,  without  interrupting  the  current,  by  another  small  beaker 
containing  water  faintly  acidified  with  sulphuric  acid,  the  cathode  being 
detached  after  some  time  and  washed  first  with  water,  then  with  alcohol, 
and  lastly  with  ether  ;  it  is  then  dried  at  70°  and  weighed.  The  increased 
weight  represents  copper  and  any  silver  present  ;  the  latter  metal  is  deter- 
mined as  in  9  (below).1 

If  the  copper  deposited  is  not  of  a  good,  brilliant  colour,  but  appears 
brownish  and  spotted  (presence  of  arsenic  or  bisrr  uth),  it  is  redissolved  in 
a  mixture  of  5-7  c.c.  of  cone,  sulphuric  acid  and  15-20  c.c.  of  nitric  acid 
(D  1-33),  diluted  to  250-300  c.c.  and  again  electrolysed  with  addition  of  a 
little  powdered  lead  sulphate  (0-4  gram)  and  ferric  sulphate  (0-5  gram) 
to  prevent  traces  of  arsenic  and  bismuth  from  being  deposited  with  the 
copper. 

The  residual  liquid  free  from  copper,  together  with  the  wash  water, 
serves  for  the  determination  of  antimony  (see  5). 

2.  Determination  of  the  Bismuth.2 — (a)  ELECTROLYTICALLY.  10 
grams  of  the  sample  are  dissolved  in  50  c.c.  of  nitric  acid  (D  1-33),  10  c.c. 
of  sulphuric  acid  being  added  when  the  action  is  complete  and  the  solution 
evaporated  to  dryness.  The  residue  is  taken  up  in  200  c.c.  of  water  con- 
taining 5  c.c.  of  sulphuric  acid,  the  liquid  being  heated  to  boiling  and  the 
boiling  liquid  treated  with  10  c.c.  of  phosphoric  acid  (D  1-71).  When  cold 
it  is  mixed  with  30  c.c.  of  alcohol  and,  after  12  hours,  filtered  by  decanta- 
tion.  The  precipitate,  which  contains  all  the  lead  and  bismuth  of  the 
sample,  is  washed  first  with  a  solution  containing  by  volume  about  i% 
of  sulphuric  acid,  5%  of  phosphoric  acid  and  15%  of  alcohol,  and  then  with 
a  dilute  solution  of  ammonium  sulphide  and  potassium  cyanide  3  to  remove 
the  last  traces  of  copper,  arsenic,  antimony,  etc.  The  precipitate  is  then 
dissolved  in  the  hot  in  nitric  acid  diluted  with  an  equal  volume  of  water, 
the  liquid  filtered  by  decantation  and  the  residue  treated  with  aqua  regia 
diluted  with  an  equal  volume  of  water,  filtered  and  washed  with  boiling 
water.  The  solution  is  evaporated  with  12  c.c.  of  sulphuric  acid  until 
copious  white  fumes  of  sulphuric  acid  appear  and,  when  cold,  is  treated 

1  In  presence  of  large  quantities  of  silver,  the  electrolysis  should  be  started  at  30° 
with  a  current  of  o-i  amp.  to  deposit  all  the  silver  first.     After  some  hours  the  current 
intensity  is  raised  to  0-5-1  amp.  and  the  electrolysis  continued  at  the  ordinary  tem- 
perature until  all  the  copper  is  deposited. 

2  Detection  of  bismuth  in  copper  (Abel  and  Field).— About  6  grams  of  the  sample  are 
dissolved  in  nitric  acid,  treated  with  about  0-3  gram  of  lead  nitrate  dissolved  in  a  little 
water,  with  ammonia  until  the  reaction  is  alkaline  and  with  a  little  ammonium  carbonate. 
After  standing  a  little  while,  the  liquid  is  filtered,  the  precipitate  washed  with  ammonia- 
cal  water  and  dissolved  in  hot  acetic  acid,  and  sufficient  potassium  iodide,  dissolved  in  a 
little  water,  added  to  dissolve  in  the  hot  the  precipitate  at  first  formed.     As  it  cools,  the 
solution  deposits  lead  iodide  crystals  which,  instead  of  pale  yellow,  are  orange  or  red 
in  presence  of  bismuth.     By  this  method,  0-02  m.  grm.  of  bismuth  is  detectable.     A 
blank  experiment  with  pure  lead  nitrate  should  be  made  and  the  colour  of  the  lead 
iodide  compared  with  that  obtained  in  presence  of  the  copper. 

3  100  c.c.  of  this  solution  should  contain  5  grams  of  potassium  cyanide  and  5  c.c. 
of  ammonium  sulphide  prepared  by  saturation  of  10%  ammonia  with  hydrogen  sulphide. 


2i6  COPPER 

with  about  100  o.c.  of  water  containing  a  little  alcohol.  The  liquid  is 
filtered,  the  filter  washed  with  water  acidified  with  sulphuric  acid  and  con- 
taining alcohol  (in  all  35  c.c.  of  alcohol  should  be  used)  and  the  liquid,  about 
300  c.c.  in  volume,  electrolysed  to  determine  the  bismuth.1  ND]00,  i.e., 
current  per  loo  sq.  cm.  of  electrode  surface,  =  o-i  amp.  ;  duration  = 
about  48  hours  ;  maximum  quantity  of  bismuth  which  can  be  deposited 
=  o-i  gram. 

(b)  GRAViMETRicALLY.2  io  grams  of  the  sample  are  dissolved  in  60 
c.c.  of  nitric  acid  (D  1-3)  and  the  excess  of  acid  expelled  by  evaporation  on 
a  water-bath.  The  residue  is  dissolved  in  400  c.c.  of  water  and  neutralised, 
with  continual  shaking,  by  means  of  a  very  dilute  solution  of  sodium 
hydroxide.  As  the  acidity  diminishes,  more  and  more  dilute  alkali  should 
be  used  in  order  to  prevent  separation  of  large  clots  of  copper  hydroxide. 
A  slight  excess  of  the  alkali  is  added  so  as  to  produce  a  faint  permanent 
turbidity,  the  liquid  being  made  up  to  a  litre  and  heated  for  an  hour  on 
the  water-bath,  a  few  drops  of  the  alkali  solution  being  added  should  the 
turbidity  tend  to  disappear.  A  little  further  sodium  hydroxide  solution 
is  then  added  to  form  a  just  perceptible  precipitate  and,  after  15-20  hours, 
the  precipitate — containing,  besides  copper,  all  the  bismuth,  iron,  etc., 
of  the  sample — is  collected  on  a  filter,  washed  with  cold  water  and  dis- 
solved in  hot  dilute  hydrochloric  acid.  The  bismuth  is  precipitated  by 
rendering  alkaline  with  ammonia,  the  excess  of  which  is  expelled  on  the 
water-bath  (the  copper  should  not  precipitate),  and  the  precipitate  filtered 
off  and  washed  with  hot  water.  The  precipitated  bismuth  hydroxide  is 
redissolved  in  hydrochloric  acid,  the  liquid  diluted  and  precipitated  with 
hydrogen  sulphide,  the  precipitate  filtered  off  and  washed  with  yellow 
ammonium  sulphide  to  dissolve  any  traces  of  antimony  present  and  then 
with  water.  The  bismuth  sulphide  is  then  dissolved  in  nitric  acid  and 
reprecipitated  with  ammonia,  the  precipitate  filtered  off,  washed,  dissolved 
in  nitric  acid  and  the  solution  evaporated  in  a  tared  porcelain  crucible,  the 
bismuth  oxide  being  gently  heated  and  weighed  :  Bi2O3  X  0-8965  —  Bi. 

3.  Determination  of  the  Arsenic. — 5  grams  of  the  sample3  in 
fine  borings  are  introduced  into  the  flask  used  for  arsenic  distillation  (see 
Iron,  6)  and  are  gently  shaken  while  100-125  c.c.  of  cone,  hydrochloric  acid 
containing  in  solution  50  grams  of  ferric  chloride  free  from  arsenic  *  are 
added  through  a  long-stemmed  funnel.  The  flask  is  closed  with  the  stopper 
carrying  the  pressure-regulating  apparatus,  connected  with  the  pipette 
dipping  into  the  ammonia  solution,  and  heated  gently  to  dissolve  the  metal 
completely  ;  the  flame  is  then  increased  and  distillation  carried  on  until 
the  ammoniacal  solution  becomes  faintly  acid.  At  this  point  the  distilla- 
tion is  suspended,  the  pipette  removed  and  washed,  and  the  arsenic  deter- 
mined iodometrically  as  indicated  on  p.  179. 

1  The  lead  sulphate  which  separates,  dissolved  in  nitric  acid  containing  a  little  am- 
monium nitrate  and  copper  nitrate  (67  c.c.  of  nitric  acid  of  D  1-33,  40  c.c.  of  ammonia 
of  D  0-923  and  2-3  grams  of  copper  nitrate),  may  be  electrolysed  to  determine  the  leap 
(see  6). 

2  Lunge  :    Technical  Methods  of  Chemical  Analysis  (London,  1911),  Vol.  II,  p.  199. 

3  With  highly  arsenical  copper,  smaller  quantities  (1-2  grams)  are  used  and   io 
grams  of  ferric  chloride  are  dissolved  in  the  hydrochloric  acid  per  gram  of  metal  taken. 

*  The  purity  of  the  reagents  is  ascertained  by  a  blank  test. 


COPPER  217 

4.  Determination  of  the  Phosphorus. — 10-20  grams  of  the  sample 
are  dissolved  in  nitric  acid,  the  excess  of  the  latter  expelled,  and  the  liquid 
treated  with  i  c.c.  of  ferric  chloride  solution  free  from  phosphorus  and 
rendered  alkaline  with  ammonia.     The  precipitate  is  filtered  off,  washed 
and  dissolved  in  hydrochloric  acid,  and  the  acid  solution  treated  as  described 
on  p.  174  or,  if  in  presence  of  arsenic,  on  p.  176. 

5.  Determination  of  the  Antimony   (Classen). — The  solution  from 
which  the  copper  has  been  removed  electrolytically  as  in  i,  together  with 
the  washing  water  from  the  small  beaker,  is  evaporated  until  the  nitric 
acid  is  completely  expelled  ;  if  the  anode  is  brown,  it  is  kept  immersed  for 
some  time,  a  few  drops  of  hydrogen  peroxide  being  added  to  dissolve  the 
peroxides  deposited  on  it.1    The  solution  is  diluted  with  water  and  sub- 
jected to  the  action  of  hydrogen  sulphide  in  the  cold  to  prevent  the  pre- 
cipitation of  the  arsenic.      The  precipitate  is  filtered  off  and  washed,  and 
the  antimony  oxide  and  sulphide  and  any  tin  oxide  and  sulphide  dissolved 
in  80  c.c.  of  sodium  sulphide  solution  (D  1-225),  4~5  grams  of  potassium 
cyanide  being  added  to  the  solution  and  the  latter  electrolysed  in  the  Classen 
dish.     ND100  =  0-15  amp.  ;    duration  =  10-15  hours. 

6.  Determination  of    the  Lead   (by    electrolysis}. — 5    grams    of    the 
sample  are  treated  with  20-30  c.c.  of  nitric  acid  (D  1-18),  the  nitrous  fumes 
expelled  by  boiling  and  the  liquid  diluted  to  250-300  c.c.  and  electrolysed, 
with  a  Winkler  cathode  and  a  tared  gauze  cylinder  anode,  as  described  on 
p.  210.     ND100  =  0-5-1  amp.,  duration  =  10-15  hours. 

Whilst  copper  is  deposited  on  the  cathode,  lead  is  deposited  as  peroxide 
on  the  anode.  At  the  end  of  the  electrolysis,  the  electrodes  are  removed 
and  washed  with  water,  and  the  anode,  after  further  washing  with  dis- 
tilled water,  dried  at  180-200°,  cooled  and  weighed  :  PbO2  X  0-866  =  Pb. 

If  manganese  and  considerable  quantities  of  bismuth  and  iron  are 
present,  small  amounts  of  the  oxides  of  these  metals  are  deposited  on  the 
anode  with  the  lead  peroxide.  In  such  case  the  deposit  is  dissolved  in 
nitric  acid  containing  a  little  alcohol,  the  solution  being  evaporated  with 
sulphuric  acid  until  copious  white  fumes  appear,  the  residue  being  taken 
up  in  water,  a  little  alcohol  added,  and  the  lead  sulphate  separated  and 
weighed.  Another  method  consists  in  employing,  for  the  determination 
of  the  lead,  the  lead  sulphate  which  separates  during  the  necessary  pro- 
cedure for  the  electrolytic  determination  of  the  bismuth  (see  2,  a). 

7.  Determination  of  the  Sulphur. — The  solution  freed  from  copper 
and  lead  by  electrolysis  (see  6)  is  evaporated  to  dryness  (to  fix  the  sulphuric 
acid  it  is  advisable  to  add  a  little  sodium  carbonate).     The  residue  is  taken 
up  twice  in  hydrochloric  acid,  the  liquid  being  evaporated  to  dryness  each 
time  to  expel  the  whole  of  the  nitric  acid.     The  final  residue  is  then  dis- 
solved in  5  c.c.  of  cone,  hydrochloric  acid  and  50  c.c.  of  hot  water  and  barium 
chloride  added  to  the  clear  liquid  thus  obtained  to  precipitate  the  sulphuric 
acid  formed  by  oxidation  of  the  sulphur  during  the  attack  of  the  metal, 
the  ordinary  conditions  being  observed. 

8.  Determination    of    the    Iron,    Nickel    and    Zinc. — 5  grams  of 

1  In  case  the  copper  has  been  deposited  twice,  the  solution  from  the  second 
deposition  must  also  be  added. 


218  COPPER 

the  sample  are  treated  with  5-6  c.c.  of  sulphuric  acid  and  15-20  c.c.  of 
nitric  acid,  the  liquid  being  diluted  to  250-300  c.c.  and  electrolysed  to 
eliminate  the  copper  (see  i).  The  electrodes  are  then  removed  and  washed 
with  water,  and  the  solution  evaporated  until  the  nitric  acid  is  completely 
expelled.  If  the  anode  appears  brown,  it  is  left  for  some  time  immersed  in 
the  evaporating  liquid,  the  peroxides  deposited  on  it  being  caused  to  dis- 
solve by  addition  of  a  few  drops  of  hydrogen  peroxide.  When  cold  the 
residue  is  dissolved  in  water  and  the  solution  treated  in  the  hot  with  hydro- 
gen sulphide  to  precipitate  the  arsenic,  lead,  antimony,  etc.  The  precipitate 
is  filtered  off  and  washed,  and  the  filtrate  boiled  to  expel  the  hydrogen 
sulphide,  treated  with  1-2  c.c.  of  hydrogen  peroxide,  boiled  and  rendered 
alkaline  with  ammonia  to  precipitate  the  iron.  When  considerable  quan- 
tities of  iron  are  present,  it  is  advisable  to  repeat  this  precipitation  after 
solution  of  the  precipitate  in  a  little  hot,  dilute  sulphuric  acid.  The  fernc 
hydroxide  separated  is  washed,  dried  and  ignited  ;  it  may  be  weighed 
directly  or  dissolved  in  a  little  dilute  sulphuric  acid  and  estimated  electro- 
lytically  (see  p.  200). 

The  filtrate,  or  the  mixed  filtrates  from  the  two  precipitations,  are  used 
for  the  electrolytic  determination  of  the  nickel  and  zinc.  First,  30-40  c.c. 
of  ammonia  and  a  few  crystals  of  hydroxylamine  sulphate  are  added  and 
the  nickel  then  deposited,  the  zinc  being  determined  in  the  residual  solution 
(see  Analysis  of  Argentan). 

When  determination  of  the  zinc  is  not  required,  the  nickel  may  be  pre- 
cipitated directly  in  the  iron-free  alkaline  solution  by  alcoholic  dimethyl- 
glyoxime  solution  (see  Gravimetric  Analysis  of  Argentan). 

9.  Determination  of  the  Silver. — 2-5  grams  of  the  sample  are  dis- 
solved in  100  c.c.  of  nitric  acid  diluted  with  an  equal  volume  of  water,  the 
solution  being  boiled  to  expel  nitrous  vapours  and,  without  filtering,  heated 
to  95°  and  treated  with  a  few  drops  of  hydrochloric  acid  to  precipitate  the 
silver.     The  liquid  is  heated  on  the  water-bath  to  separate  the  precipitate, 
which  is  filtered  off  and  washed  with  hot  water,  the  silver  being  determined 
in  this  impure  silver  chloride  either  electrolytically  or  gravimetrically. 

(a)  ELECTROLYTIC  METHOD.     The  precipitate  is  dissolved  in  the  hot 
in  120  c.c.  of  10%  potassium  cyanide  solution,  then  diluted  to  300  c.c. 
and  electrolysed  with  a  current  of  o-i  ampere. 

(b)  GRAVIMETRIC  METHOD.     The  silver  chloride  is  dissolved  in  ammonia 
by  digestion  in  the  hot  for  some  time,  the  solution  being  filtered  and  acidified 
with  nitric  acid  to  reprecipitate  the  silver  chloride,  which  is  weighed  as 
usual. 

10.  Determination  of  the  Total   Oxygen. — The  oxygen  present  in 
commercial  copper  occurs  largely  as  cuprous  oxide  and  partly  in  combina- 
tion with  extraneous  metals.     It  is  determined  by  causing  it  to  combine 
with  hydrogen  at  a  high  temperature  and  estimating  the  water  formed. 
A  condition  essential  to  accuracy  is  that  the  hydrogen  must  be  perfectly 
dry  and  free  from  oxygen. 

The  hydrogen,  made  in  a  Kipp  apparatus  from  pure  zinc  and  dilute 
sulphuric  acid,  is  purified  by  passing  it  successively  through  alkaline  pyro- 
gallol,  permanganate  solution  and  cone,  sulphuric  acid.  Any  traces  of 


COPPER  219 

oxygen  still  present  are  eliminated  by  passing  the  gas  through  a  glass  or 
porcelain  tube  containing  platinised  asbestos  heated  to  redness,  the  water 
formed  being  absorbed  by  means  of  a  U-tube  charged  with  phosphoric 
anhydride. 

Prior  to  the  determination,  a  blank  test  is  made,  the  hydrogen  being 
passed  through  the  glass  or  porcelain  tube  to  be  used  in  the  determination 
and  arranged  on  a  combustion  furnace  ;  after  about  10  minutes,  a  tared 
phosphoric  anhydride  tube,  full  of  hydrogen  and  connected  with  a  calcium 
chloride  tube  to  keep  atmospheric  moisture  away,  is  attached,  the  tube 
being  then  heated  to  redness  and  the  stream  of  hydrogen  continued  for 
about  an  hour.  At  the  end  of  this  time  the  burners  are  extinguished  and 
the  tube  allowed  to  cool  in  the  current  of  hydrogen  ;  the  U-tube  should 
exhibit  no  appreciable  increase  in  weight. 

For  the  determination,  10  grams  of  the  sample,  freed  from  grease  and 
any  traces  of  iron  (see  i)  are  weighed  in  a  perfectly  dry  porcelain  boat, 
which  is  placed  in  the  cold,  dry  combustion  tube,  the  air  being  then  expelled 
by  passing  hydrogen  for  10-15  minutes.  The  phosphoric  anhydride  tube 
and  its  calcium  chloride  tube  are  then  attached  and  the  tube  heated  strongly 
near  the  boat  for  20-30  minutes. 

When  the  reduction  is  complete,  the  tube  is  allowed  to  cool  in  the  current 
of  hydrogen  and  the  phosphoric  anhydride  tube  weighed  ;  the  increased 
weight  represents  water,  and  this  should  correspond  with  the  oxygen  lost 
from  the  metal  in  the  boat. 

The  determination  of  oxygen  in  copper  is  a  very  delicate  and  perhaps  not 
quite  exact  operation.  Metallographic  examination  gives  information  in  this 
respect. 

*** 

Copper  of  good  quality  should  be  bright  red  and  very  ductile  and  malleable  ; 
its  fracture  should  be  finely  granular,  of  uniform  colour  and  free  from  spots  ; 
its  specific  gravity  should  lie  between  8-65  and  8-93,  and  it  should  contain  more 
than  99-5%  Cu  (electrolytic  copper  may  contain  99-8-99-9%  or  even  more). 
As  the  purity  diminishes,  the  specific  gravity,  malleability  and  ductility 
decrease. 

Of  the  likely  impurities,  those  of  special  influence  on  the  mechanical  pro- 
perties are  bismuth,  lead,  antimony,  sulphur,  arsenic,  phosphorus,  nickel,  iron 
and  oxygen. 

According  to  Hampe,  the  presence  of  0-02%  Bi  is  sufficient  to  render  copper 
brittle  in  the  hot,  while  0*05%  makes  it  brittle  also  in  the  cold.  Keller  states 
that  copper  containing  a  few  thousandths  of  bismuth  is  unsuitable  for  electrical 
conductors  ;  a  similar  effect  is  exerted  by  lead  in  the  proportion  of  0-3-0-4%. 
Antimony  was  once  regarded  as  highly  injurious,  but  less  than  0-5%  appears 
innocuous  ;  in  whatever  proportion,  it  lowers  the  electrical  conductivity,  and 
copper  containing  antimony  is  unfit  for  making  brass.  Sulphur,  which  may  be 
present  as  cuprous  sulphide,  renders  it  cold  short  if  present  in  greater  quantity 
than  0-5%.  On  the  other  hand,  phosphorus  and  arsenic  in  small  proportions 
(not  more  than  0-5%)  make  it  more  tenacious  and  resistant,  because  they  impede 
the  formation  of  cuprous  oxide,  0-5%  of  which  greatly  diminishes  the  tenacity 
and  ductility  (some  types  of  copper  may  contain  even  more,  electrolytic  copper 
according  to  Keller,  as  much  as  0-6-0-8%).  On  this  account,  certain  railway 
companies  use  for  their  locomotive  boilers  copper  containing  not  less  than  0-2- 
°*J%  °f  arsenic.  Small  proportions  of  iron  and  nickel  may  often  be  found  in 


22O 


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CUPRO-SILICON  221 

commercial  copper  and  do  not  modify  its  properties  appreciably,  provided  their 
amount  does  not  exceed  0-3-0-4%. 

Compositions  of  the  commoner  commercial  coppers  are  given  in  Table  XXI 
(Hollard,  Schnabel,  Hampe) . 


PHOSPHOR-COPPER 

Phosphor-copper  is  usually  employed  as  a  deoxidiser  and  for  the  prepara- 
tion of  phosphor  bronzes.  It  occurs  mostly  in  cakes  of  metallic  appear- 
ance and  bronze  or  steel-grey  colour  and  sometimes  with  bluish  reflections  ; 
it  is  brittle  and  has  a  crystalline  structure. 

Its  analysis  comprises  essentially  determinations  of  the  phosphorus 
and  copper.  The  impurities,  derived  from  those  of  the  copper  used  in  its 
preparation,  may  be  estimated  by  the  methods  given  on  p.  214  for  the 
analysis  of  commercial  copper. 

1.  Determination  of  the  Phosphorus. — o'5  gram  of  the  finely  pow- 
dered sample  are  treated  in  a  covered  dish  with  10  c.c.  of  nitric  acid  (D  1-4), 
gentle  heat  being  applied  when  the  action  slackens.     If  any  unattacked 
metal  remains  after  about  30  minutes,  a  few  drops  of  hydrochloric  acid 
are  occasionally  added  and  the  liquid  heated  until  solution  is  complete 
and  then  evaporated  to  dryness  with  10  c.c.  of  nitric  acid.     The  residue 
is  extracted  with  hot  water  acidified  with  nitric  acid  and  the  liquid  filtered 
to  separate  (and  determine,  if  necessary)  any  traces  of   silica  present,  the 
filtrate  being  made  up  to  250  c.c. 

50  c.c.  of  this  solution  are  evaporated  to  10  c.c.  and  treated  with 
150  c.c.  of  ammonium  molybdate  solution,  the  remaining  procedure  being 
as  in  the  determination  of  phosphorus  in  iron  (q.v.). 

2.  Determination  of  the  Copper. — i  gram  of  the  sample  is  treated 
with  10  c.c.  of  nitric  acid  (D  1-2)  and  5  c.c.  of  hydrochloric  acid  in  a  covered 
beaker.     The  solution  is  evaporated  witfr  2-3  c.c.  of  sulphuric  acid  until 
the  nitric  and  hydrochloric  acids  are  completely  expelled  and  then  heated 
on  a  sand-bath  until  white  fumes  of  sulphuric  acid  appear.     When  cool 
the  residue  is  taken  up  in  hot  water,  the  solution  being  mixed  with  5-6  c.c. 
of  nitric  acid  (D  1-4),  made  up  to  200-250  c.c.  and  electrolysed  (see  p.  214)  : 
Winkler  electrodes  ;  ND100  =  0-3-0-4  amp.  ;  duration  =  10-15  hours. 

Phosphor-copper  usually  contains  9-15%  P  (sometimes,  however,  only  0-5- 
5%).  Preference  is  given  in  practice  to  products  with  10%  P. 


CUPRO-SILICON 

Cupro-silicon  or  copper  silicide,  also  improperly  termed  silicon  bronze, 
is  prepared  in  the  electric  furnace  by  reducing  silica  with  carbon  in  presence 
of  copper.  It  is  used  especially  for  the  deoxidation  of  brasses  and  bronzes 
and  for  the  preparation  of  copper-silicon  alloys  containing  small  quantities 
of  silicon  and  used  in  electro-technics  for  telephone  wires,  cables,  etc.  (alloys 
with  0-2-3-5%  Si). 

Its  analysis   comprises    essentially  determinations   of    the  silicon  and 


222  CUPRO-MANGANESE 

copper  ;    the  impurities  may,  if  required,  be  estimated  as  in  commercial 
copper  (see  p.  215). 

1.  Determination    of   the    Silicon. — i  gram   of  the  finely  powdered 
sample  is  treated  with  10-20  c.c.  of  nitric  acid  (D  1-4)  and  heated  for  a 
long  time.     After  addition  of  1-2  c.c.  of  hydrochloric  acid,  it  is  again  heated 
for  a  short  time  and  finally  evaporated  in  presence  of  2  c.c.  of  sulphuric 
acid.     The  heating  is  continued  on  a  sand-bath  until  copious  white  fumes 
of  sulphuric  acid  are  emitted,  the  cooled  residue  being  treated  with  hot 
water,  filtered,  and  the  filter  thoroughly  washed  with  hot  water  acidified 
with  sulphuric  acid.     The  filter,   still  somewhat  moist,   is  placed  point 
upwards  in  a  platinum  crucible  and  the  latter  covered  and  heated,  at  first 
gently  and  later  to  ignition,  the  subsequent  procedure  being  that  followed 
in  estimating  silicon  in  iron  or  steel  (see  p.   171). 

2.  Determination   of  the   Copper. — The  filtrate  from  the  silica  is 
acidified  with  5-6  c.c.  of  nitric  acid,  made  up  to  250-300  c.c.  and  electrolysed 
to  determine  the  copper.      Winkler  electrodes  ;    ND100  =  0-3-0-4  amp.  ; 
duration,  10-15  hours. 

The  commoner  commercial  types  of  cupro-silicon  contain  10,  15,  20  and  35% 
of  silicon. 


CUPRO-MANGANESE 

The  copper-manganese  alloys  are  used  as  deoxidisers  of  copper,  and 
for  the  preparation  of  copper-manganese  alloys  with  a  low  content  of  man- 
ganese— so-called  manganese  bronzes — and  of  the  manganese  brasses  and 
true  manganese  bronzes.  Analysis  includes  determination  of  the  copper 
and  manganese  and,  sometimes,  of  the  impurities,  particularly  the  silicon, 
lead,  iron  and  nickel. 

1.  Determination  of  the  Copper. — i  gram  of  the  sample  is  treated 
in  a  covered  dish  with  10-15  c.c.  of  nitric  acid  (D  1-2),  6  c.c.  of  dilute  sul- 
phuric acid  (i  vol.  acid  to  i  vol.  water)  being  added  when  the  action  is 
complete  and  the  liquid  evaporated  on  a  water-bath  to  eliminate  the  nitric 
acid  and  then  heated  on  a  sand-bath  until  copious  white  fumes  of  sulphuric 
acid  appear.  When  cool,  the  residue  is  stirred  and  gently  heated  with 
30  c.c.  of  water  to  dissolve  the  copper  and  manganese  sulphates,  5  c.c.  of 
95%  alcohol  being  added  and  the  mixture  left  for  one  or  two  hours.  Any 
insoluble  residue,  consisting  usually  of  silica  and  lead  sulphate,  is  filtered 
off  and  washed  with  a  mixture  of  60  c.c.  of  water,  10  c.c.  of  alcohol  and  0-5 
c.c.  of  sulphuric  acid,  the  filtrate  being  evaporated  almost  to  dryness  to 
expel  all  the  alcohol,  and  the  residue  taken  up  in  water,  diluted  to  150  c.c., 
heated  to  60-70°  and  electrolysed  to  determine  the  copper  :  Winkler  elec- 
trodes ;  temperature  =  60-70°  ;  ND108  =  0-2-0-3  amp.  ;  duration  = 
6-7  hours. 

When  the  whole  of  the  copper  is  deposited  the  solution  is  allowed  to 
cool  a  little,  the  cover-glasses  removed  from  the  beaker,  the  latter  slowly 
lowered  and  the  electrodes  washed  with  water  as  they  emerge.  The  cathode 
is  then  washed  with  water,  alcohol  and  ether,  dried  at  70°  and  weighed. 


CUPRO-MANGANESE  223 

2.  Determination   of  the  Iron  and  Manganese. — The  liquid  from 
which  the  copper  has  been  removed  is  treated  with  2-3  drops  of  hydrogen 
peroxide,  the  anode  being  kept  immersed  to  dissolve  the  coating  of  man- 
ganese dioxide.     The  liquid  is  boiled  for  a  few  moments,  the  electrode 
withdrawn  and  washed  with  water  and  the  solution,  when  cold,  made  up 
to  volume  in  a  300  c.c.  flask.     In  aliquot  parts  the  iron  and  manganese 
are  determined  either  volumetrically  or  electrolytically. 

(a)  VOLUMETRIC  METHOD.     In  50  or  100  c.c.  the  iron  is  determined  by 
titration  with  permanganate  after  reduction  with  amalgamated  zinc.1     In 
another  aliquot  part  (50  or  100  c.c.  according  to  the  amount  of  manganese 
present),  the  manganese  is  titrated  by  Volhard's  volumetric  method  (see 
Ferro-manganese) . 

(b)  ELECTROLYTIC  METHOD.     In  100-200  c.c.,  according  to  the  amount 
of  manganese  present,  the  iron  and  manganese  are  estimated  as  described 
for  ferro-manganese. 

3.  Determination  of  the  Nickel. — -In  an  aliquot  part  of  the  300  c.c. 
of  solution  (see  2),  the  nickel  is  determined  by  means  of  dimethylglyoxime 
in  presence  of  the  necessary  quantity  of  tartaric  acid  (see  Nickel  Steel). 

[•  4.  Determination  of  the  Silicon  and  Lead. — The  residue  remaining 
on  the  filter  when  the  copper  and  manganese  sulphates  are  taken  up  in 
water  (see  i)  contains  all  the  silicon  and  lead  of  the  sample  as  silica  and 
lead  sulphate.  The  latter  is  now  dissolved  in  nitric  acid  containing  ammo- 
nium nitrate  and  the  lead  in  the  solution  determined  electrolytically  in 
presence  of  copper  nitrate  (see  Lead-tin  Alloys). 

The  residue  insoluble  in  nitric  acid  and  ammonium  nitrate  consists  of 
silica  (possibly  impure)  and  is  filtered  off,  washed,  ignited  in  a  platinum 
crucible,  weighed,  treated  with  hydrofluoric  acid  and  again  weighed  ;  the 
loss  in  weight  represents  silica  (see  Determination  of  Silicon  in  Iron). 

With  copper-manganese  alloys  containing  little  manganese  (manganese 
bronzes)  it  is  advisable  to  determine  the  copper  separately  in  two  distinct  por- 
tions (i  gram  each)  of  the  sample.  When  the  copper  is  eliminated,  the  two 
portions  of  manganese  dioxide  on  the  anodes  are  dissolved  and  made  up  together 
to  300  c.c. 

*** 

Copper-manganese  alloys  contain  about  25-30%  of  manganese  with  small 
quantities  of  iron,  silicon,  etc.  Two  principal  types  are  met  with  commercially  : 
the  so-called  impure  alloy  with  72-74%  Cu,  23-24%  Mn,  2-5-4-5%  Fe  and  0-2— 
°*5%  Si,  and  the  pure  alloy  with  70-72%  Cu,  28-30%  Mn,  o-i-o-3%  Fe  and  0-05- 
0-1%  Si. 

The  alloys  with  a  low  manganese  content  or  manganese  bronzes,  used,  owing 
to  strength  in  the  hot,  for  valves,  tie-rods  for  locomotives,  etc.,  contain  on  the 
average  4-6%  Mn  and  such  impurities  as  are  usually  met  with  in  commercial 
copper. 

1  This  may  be  prepared  by  dissolving  5  grams  of  mercury  in  25  c.c.  of  nitric  acid 
(D  1-2),  making  the  solution  up  to  about  250  c.c.,  and  immersing  500  grams  of  zinc  in 
granules  of  about  i  mm.  diameter  in  it  for  2-3  minutes  with  continual  agitation. 


224  ORDINARY  BRASSES 


ORDINARY    BRASSES 

Ordinary  brasses  are  alloys  of  copper  and  zinc  in  various  proportions 
always  containing  as  impurities  small  quantities  of  lead,  iron,  tin  and  some- 
times nickel,  arsenic,  sulphur,  phosphorus  and  bismuth.  Their  analysis 
comprises  the  determination,  by  electrolytic  or  gravimetric  methods,  of 
the  constituent  elements  and  impurities. 

A.  Electrolytic  Methods 

In  a  covered  beaker,  tall  and  narrow,  i  gram  of  the  alloy  in  turnings  or 
filings  is  dissolved  at  a  gentle  heat  in  15  c.c.  of  nitric  acid  (D  1-2). 

1.  Determination  of  the  Tin. — The  solution  is  diluted  with  30-40  c.c. 
of  water  and  if  it  appears  turbid  owing  to  the  presence  of  metastannic  acid, 
it  is  evaporated  to  dryness,  taken  up  in  a  few  drops  of  nitric  acid  and  a 
little  water,  heated  for  some  time  and  filtered,  the  insoluble  residue  being 
collected  on  a  small,  tight  filter  and  the  filtrate  in  a  350  c.c.  electrolytic 
beaker.     The  filter  is  washed,  first  with  water  faintly  acidified  with  nitric 
acid  and  then  with  water  alone,  dried,  ignited  in  a  porcelain  crucible  and 
weighed  1 :    SnO2  X  0-7881  =  Sn. 

2.  Determination  of  the  Copper  and  Lead. — The  liquid  freed  from 
the  metastannic  acid  is  treated  with  15  c.c.  of  nitric  acid  of  D  1-2  (in  absence 
of  tin,  it  is  not  necessary  to  add  fresh  acid,  since  the  evaporation  of  the 
solution  to  dryness  is  omitted),  made  up  to  about  200  c.c.,  allowed  to  cool 
and  electrolysed  to  determine  simultaneously  the  copper  and  the  lead  2  : 
Winkler  cathode  and  matte  gauze  cylinder  anode  ;   ND100  =  0-3  amp.  ; 
voltage,  1-8-2  ;    duration,  10-15  hours.     After  half  an  hour  or  an  hour, 
when  the  greater  part  of  the  lead  has  been  deposited  as  peroxide  on  the 
anode,  20  c.c.  of  10%  sulphuric  acid  are  added  to  the  electrolyte,  which  is 
carefully  stirred  by  means  of  a  glass  rod. 

When  the  deposition  of  the  copper  and  lead  is  complete,  the  electrolytic 
beaker  is  replaced,  rapidly  and  without  interruption  of  the  current,  by  a 
small,  tall  and  narrow  beaker  containing  water  acidified  with  sulphuric 
acid,  this  being  replaced  after  some  time  by  another  beaker  containing  dis- 
tilled water.  Finally  the  electrodes  are  detached  and  washed,  the  cathode 
with  water,  alcohol  and  ether,  followed  by  drying  at  70°,  and  the  anode 
with  water  alone,  followed  by  drying  at  180-200°  :  PbO2  x  0-866  —  Pb. 

3.  Determination  of  the  Iron  and  Zinc. — The  liquid  from  which 
the  copper  and  lead  have  been  separated  and  the  wash  water  from  the 
first  beaker  are  evaporated  together  until  white  fumes  of  sulphuric  acid 
are  emitted,  in  order  to  convert  the  zinc  and  iron  nitrates  into  sulphates. 
When  cold,  it  is  taken  up  in  water  acidified  with  sulphuric  acid,  a  few  drops 
of  hydrogen  peroxide  added,  the  liquid  heated  to  convert  the  basic  sulphates 

1  For  the  electrolytic  determination  of  tin,  see  Ordinary  Bronzes. 

2  If  the  alloy  contains  bismuth,  arsenic  and  manganese,  the  determination  of  the 
lead  cannot  be  effected  simultaneously  with  that  of  the  copper,  since  these  metals  may 
be  deposited  on  the  anode.     In  this  case  the  lead  must  be  determined  by  the  method 
indicated  for  the  analysis  of  delta  metal  (see  later  :  Complex  Brasses). 


ORDINARY   BRASSES  225 

into  neutral  sulphates  and  the  clear,  hot  solution  treated  with  ammonia  in 
slight  excess.  After  a  short  rest  on  the  water-bath,  the  precipitated  ferric 
hydroxide  is  filtered  off,  washed,  dried,  ignited  and  weighed  1 :  Fe2O3  X 
0-6994  =  Fe. 

The  filtrate  now  contains  only  the  zinc,  which  may  be  estimated  with 
stationary  or  rotating  electrodes  in  the  manner  described  below.  In  any 
case,  however,  if  the  brass  contains  more  than  20%  of  zinc  (shown  by  the 
weight  of  copper  obtained),  it  is  advisable  to  make  up  the  volume  of  the 
solution  to  300  c.c.  and  to  determine  the  zinc  on  150  c.c.2 

(a)  Determination  with  stationary  electrodes.     The  ammoniacal  solution 
is  acidified  with  lactic  acid,  then  rendered  faintly  alkaline  with  sodium 
hydroxide,  treated  with  3  grams  of  ammonium  oxalate    and  5  grams  of 
sodium  sulphate,  heated  gently  to  dissolve  the  salts  and  made  up  to  about 
250  c.c.      5   c.c.  of  lactic  acid  are   then  added  and  the  still  tepid  liquid 
electrolysed  :    coppered  Winkler  cathode  3  ;    Winkler  spiral  anode  ;    ND100 

=  0-5-0-6  amp.  ;  voltage  —  3-4  ;  duration,  3-4  hours.  After  about  2 
hours,  the  current  intensity  is  raised  to  i  amp.  and  2  c.c.  of  lactic  acid 
are  added,  the  electrolysis  being  continued  until  the  deposition  of  the  zinc 
is  complete. 

To  ascertain  if  all  the  zinc  is  deposited,  a  few  drops  of  the  electrolyte 
are  removed  and  treated  with  a  drop  of  potassium  ferrocyanide  :  no  tur- 
bidity should  be  produced,  even  after  some  time.  Another  method  con- 
sists in  connecting  to  the  upper  extremity  of  the  stem  of  the  cathode,  by 
means  of  a  binding  screw,  a  stout  copper  wire  previously  cleansed  by  a 
brief  immersion  in  nitric  acid,  and  bending  this  wire  twice  at  right  angles 
so  that  it  dips  into  the  electrolyte  for  a  few  centimetres  without  touching 
the  electrodes  :  if  the  wire  does  not  show  a  faint  bluish  deposit  of  zinc  after 
10-15  minutes,  the  deposition  is  complete.  The  electrolytic  beaker  is  then 
replaced  by  a  small  beaker  filled  with  distilled  water,  the  cathode  being 
detached  after  some  time,  washed  with  water,  alcohol  and  ether  and  dried 
at  70°. 

(b)  Determination  with  rotating  electrodes.     The  ammoniacal  solution  is 
acidified  with  sulphuric  acid,   rendered  alkaline  with  sodium  hydroxide 
and  then  faintly  acid  by  means  of  25%  formic  acid  solution  ;    the  liquid  is 
heated  to  40-50°  and  electrolysed  :   coppered  Winkler  cathode  3  ;   rotating 
spiral  anode  ;    rotations,  1000  per  minute  ;    temperature,    40-50° ;    ND100 

1  If  there  is  much  ferric  hydroxide,  it  is  advisable  to  precipitate  twice  to  get  rid  of 
traces  of  zinc  it  may  retain. 

2  In  the  analysis  of  white  brasses  (90-95%  Zn),  the  zinc  should  be  determined  on 
an  aliquot  part  of  the  solution  containing  about  o-2-o-3  gram  of  zinc. 

3  Coppering  of  platinum  electrodes. — In  the  electrolytic  determination  of  zinc  and 
also  in  that  of  tin,  it  is  convenient  to  use  the  coppered  cathode  because,  if  these  metals 
are  deposited  directly  on  the  platinum  they  form  alloys  with  it  and,  when  the  deposited 
metal  is  dissolved  in  acid,  the  electrode  exhibits  black  spots  difficult  to  remove. 

The  electrode  may  be  coppered  under  the  conditions  given  for  the  electrolytic  deter- 
mination of  copper,  a  solution  of  copper  sulphate  acid  with  nitric  acid  being  electrolysed 
until  the  cathode  is  uniformly  covered  with  copper.  A  more  brilliant  coating  is  obtained 
by  electrolysing,  at  ND,00  ==  i  amp.,  a  copper  sulphate  solution  treated  with  an  excess 
of  ammonium  oxalate  and  acidified  with  oxalic  acid,  at  70-80°.  The  coppered  cathode 
obtained  by  either  of  these  methods  is  washed  with  water,  alcohol  and  ether,  dried  at 
70°  and  tared. 

A.C.  15 


226  ORDINARY   BRASSES 

=  i— i '5   amp.  ;    voltage  =  4-5  ;    duration,   30-40   minutes.     During  the 
whole  course  of  the  electrolysis,  the  liquid  should  be  kept  faintly  acid. 

4.  Determination  of  the  Nickel. — In  presence  of  nickel,  the  nickel 
and  zinc  are  determined  under  the  conditions  indicated  for  the  electrolytic 
analysis  of  argentan. 

5.  Determination   of  the   Phosphorus. — See  Analysis  of  Phosphor 
Bronzes. 

6.  Determination   of  the   Arsenic,    Sulphur   and   Bismuth. — The 
methods  given  for  the  analysis  of  copper  (g.v.)  are  followed. 


B.  Gravimetric  Methods 

In  a  small  covered  beaker,  0-5  gram  of  the  sample  is  dissolved  in  10- 
15  c.c.  of  nitric  acid  (D  1-2)  at  a  gentle  heat. 

1.  Determination  of  the  Tin. — When  the  action  is  complete,   the 
solution  is  diluted  with  15-20  c.c.  of  water  and,  if  it  appears  turbid  owing 
to  the  presence  of  metastannic  acid,  evaporated  to  dryness.     The  residue 
is  heated  for  some  time  with  a  few  drops  of  nitric  acid  and  a  little  water 
and  the  metastannic  acid  filtered  off,  washed  with  hot  water  acidified  with 
nitric  acid,  ignited  and  weighed  :    Sn02  X  0-7881  =  Sn. 

2.  Determination  of  the  Lead. — The  liquid  freed  from  the  metastannic 
acid,  or  the  original  solution  if  the  alloy  does  not  contain  tin,  is  treated 
with  3-4  c.c.  of  concentrated  sulphuric  acid,  evaporated  to  dryness  and 
heated  on  a  sand-bath  until  white  fumes  of  sulphuric  acid  appear.     When 
cool,  the  residue  is  taken  up  in  50  c.c.  of  water,  gently  heated  and  stirred 
to  dissolve  the  basic  copper  and  zinc  sulphates,  allowed  to  cool  and  mixed 
with  15  c.c.  of  95%  alcohol.     After  standing  for  1-2  hours,  the  lead  sulphate 
separated  is  collected  on  a  Gooch  crucible,  washed  first  with  a  mixture  of 
60  c.c.  of  water,  10  c.c.  of  alcohol  and  0-5  c.c.  of  sulphuric  acid  and  then 
with  alcohol  until  the  filtrate  is  neutral ;   the  crucible  is   then  dried  in  an 
air-oven  in  a  roomy  porcelain  crucible  :    PbSO,,  X  0-6831  —  Pb. 

3.  Determination  of  the  Copper. — The  filtrate  from  the  lead  sulphate 
is  evaporated  until  the  alcohol  is  completely  expelled,  the  residue  being 
heated  to  boiling  with  100  c.c.  of  water  and  the  copper  precipitated  with 
hydrogen  sulphide.     The  liquid  is  decanted  on  to  a  filter  and  the  precipitate 
washed  first  with  saturated  hydrogen  sulphide  solution  containing  about 
20  c.c.   of   2N-sulphuric  acid  in  100  c.c.  and  afterwards   with   saturated 
hydrogen  sulphide  solution  alone  ;   the  precipitate  is  dried  and  the   copper 
determined  as  cuprous  sulphide  :    Cu2S  X  0-7986  =  Cu. 

4.  Determination  of  the  Iron. — The  filtrate  is  freed  from  hydrogen 
sulphide,  concentrated  to  a  small  volume,  treated  with  a  few  drops  of 
hydrogen  peroxide  to  oxidise  the  iron,  boiled  and  rendered  alkaline  with 
dilute  ammonia.     After  a  short  rest  on  the  water-bath,  the  precipitated 
ferric  hydroxide  is  filtered,  washed,  ignited  and  weighed  :    Fe2O:j  x  0-6994 
=  Fe.     If  the  amount  of  ferric  hydroxide  is  considerable,  the  precipitation 
should  be  repeated  to  get  rid  of  traces  of  zinc. 

5.  Determination  of  the  Zinc.— The  liquid  free  from  iron  is  neutralised 


SPECIAL   BRASSES  227 

exactly,  acidified  with  8-10  drops  of  2  N  -hydrochloric  acid,  heated  to  50°, 
treated  with  about  2%  (with  reference  to  the  volume  of  the  liquid)  of 
ammonium  chloride,  and  saturated  with  hydrogen  sulphide  at  50°.  When 
the  zinc  is  completely  precipitated,  the  zinc  sulphide  is  allowed  to  settle 
at  a  moderate  temperature,  and  is  then  filtered  off,  washed  with  aqueous 
hydrogen  sulphide  containing  2  grams  of  ammonium  chloride  per  100  c.c. 
and  weighed  as  zinc  sulphide,  after  being  heated  in  a  current  of  hydrogen 
in  presence  of  sulphur  :  ZnS  x  0-6709  =  Zn. 

6.  Determination  of  the  Nickel.  —  The  filtrate  from  the  zinc  precipi- 
tate is  boiled  to  expel  hydrogen  sulphide,  concentrated,  rendered  faintly 
alkaline  with  ammonia,  and  the  nickel  precipitated  with  alcoholic  dimethyl- 
glyoxime  solution  (see  Analysis  of  Nickel  Steel  and  of  Argentan). 

7.  Determination   of  the   Arsenic,    Sulphur   and   Bismuth.  —  The 
methods  given  for  the  analysis  of  copper  (q.v.)  are  followed. 

8.  Determination   of  the   Phosphorus.  —  See  Analysis  of  Phosphor 
Bronze. 


The  ordinary  brasses,  besides  copper  and  zinc,  often  contain  small  quan- 
tities of  lead  and  iron  (sometimes  up  to  i%),  in  some  cases  tin  (0-5-1%)  and 
nickel  (0-1-0-3%)  and,  in  general,  the  impvirities  present  in  the  copper  and  zinc 
used  in  their  preparation. 

A  good  brass  should  exhibit  a  fracture  of  uniform  colour  and  fine  and  homo- 
geneous grain.  It  should  not  contain  more  than  0-01%  of  antimony,  as  other- 
wise it  is  brittle  and  unfit  for  hammering  ;  it  should  not  contain  more  than 
c-oi%  of  bismuth  or  0-1%  of  arsenic. 

The  mean  percentage  compositions  of  some  of  the  commoner  commercial 
brasses  are  as  follows  : 

TABLE   XXII 
Composition  of  Brasses 


Variety. 

Cu 

Zn 

Pinchbeck,  tombac,  Mannheim  gold  (for  cheap  jewellery) 
Brass  for  sheets  and  plates     

85-95 
60—72 

5-15 
28   40 

Brass  for  tubes  

6s—  7o 

Brass  for  casting      

66-67 

Brass  for  wire    

60—67 

°,3—  4.O 

White  brasses  (Fontainmoreau  bronzes)       .... 
Brasses  for  welding       

I-IO 
0,4.—  OO 

90-991 
10-66  2 

SPECIAL    BRASSES 

By  this  name  are  indicated  those  alloys  of  copper  and  zinc  which  con- 
tain small  quantities  of  one  or  more  other  elements  (especially  lead,  tin, 
iron,  manganese,  aluminium)  introduced  for  the  purpose  of  imparting 
special  properties.  The  most  important  are  as  follows. 

1  Often  contains  1-2%  of  lead. 

2  Sometimes  contains  also  small  quantities  of  tin, 


228 


SPECIAL  BRASSES 


Lead  Brasses. 

Lead  brasses  are  very  soft  and  therefore  suitable  for  castings  to  be 
worked  at  the  lathe.  Their  analysis  comprises,  besides  determinations  of 
copper  and  zinc,  also  that  of  lead  and  of  the  impurities  usually  occurring 
in  ordinary  brass  (iron,  tin,  nickel,  sulphur,  phosphorus,  arsenic,  bismuth, 
etc.).  The  analytical  methods  are  exactly  those  used  for  ordinary  brass 
(q.v.). 


*  * 


Lead  brasses  usually  contain  1-3%  of  lead  and  such  impurities  as  are  found 
in  common  brass. 


Tin  Brasses 

Tin  brasses  are  used  especially  for  making  tubes,  plates,  valves,  etc., 
for  naval  construction.     They  are  analysed  by  the  same  methods  as  ordinary 

brass  (q-v.). 

* 
*  * 

Tin  brasses  contain  on  the  average  60-62%  Cu,  37-5-39%  Zn  and  1-1-5% 
Sn.     In  this  category  fall  Naval  brass,  Iton  brass  and  Laveyssi&re  bronze. 


Manganese  Brasses 

Manganese  is  introduced  in  small  quantities  into  brass  to  increase  the 
strength,  elasticity  and  hardness.  The  constituents  of  these  brasses  are 
determined  as  with  the  complex  brasses  (see  later). 

* 
*  * 

The  two  types  in  most  common  use  have  the  compositions  :  (i)  59-60%  Cu, 
40-41%  Zn,  traces  of  Mn,  and  (2)  58-59%  Cu,  39-40%  Zn,  1-8-2-2%  Mn.  They 
are  used  in  marine  construction,  especially  for  making  propellers. 

The  following  table  gives  the  compositions  prescribed  for  manganese  brasses 
by  the  American  Society  for  the  Testing  of  Materials  and  by  the  Technical  Bureau 
for  Steam  Plant  of  the  United  States  Navy  (Industria,  1914)  : 


TABLE  XXIII 
Compositions  of  Manganese  Brasses 


Zn 

Sn 

Fe 

Al 

Mn 

Pb 

(max.) 

(max.) 

(max.) 

(max.) 

(max.) 

American    Society    for    the 

Testing  of  Materials  . 

55-60 

39-45 

2 

2 

0-5 

0-5 

— 

Technical  Bureau  for  Steam  ) 

57-60 

37-40 

o-75 

I 

0-50 

0-30 

— 

Plant  of  U.S.  Navy     .       / 

56-68 

40-42 

J 

I 

0-50 

0-30 

O-2O 

COMPLEX   BRASSES  229 

Iron  Brasses 

The  addition  of  small  quantities  of  iron  imparts  to  brass  properties 
analogous  to  those  of  manganese  brasses,  and  iron  brasses  have  the  same 
applications  as  the  latter.  The  analytical  procedure  is  that  indicated  for 
common  brass  (q.v.). 


* 
*  * 


The  iron  brasses  in  more  common  use  have  the  following  mean  compositions  : 
Sterro  metal:   55-60%  Cu,  38-42%  Zn,  1-5-2%  Fe,  0-0-8%  Sn. 
Aich's  metal :   58-60%  Cu,  36-41%  Zn,  0-7-1-8%  Fe,  0-1%  Sn. 


Aluminium  Brasses 

Aluminium  brasses  have  properties  similar  to  those  of  manganese  and 
iron  brasses  and  find  the  same  uses  in  naval  construction.  They  are  analysed 
by  the  methods  for  complex  brasses  (q.v.). 


The  aluminium  brasses  in  more  common  use  have  the  following  mean  per- 
centage compositions  (Guillet)  : 

(1)  Copper,  68-70  ;    zinc,  31-27  ;    aluminium,  3-1. 

(2)  „         64-66;       „      33-30;  „  4-1. 

(3)  » 


COMPLEX    BRASSES 

Complex  brasses  have  properties  very  similar  to  those  of  manganese 
brasses  and  are  largely  used,  particularly  for  making  propellers,  anchors, 
keels,  torpedo  tubes,  etc. 

These  brasses  may  contain  at  the  same  time  :  iron  and  manganese  ; 
iron  and  aluminium  ;  iron,  manganese,  aluminium  and,  sometimes,  tin. 
Their  analysis  includes  determinations  of  the  components  proper  (Cu,  Zn, 
Mn,  Fe,  Al,  Sn)  and  of  any  extraneous  elements  present  as  impurities  (Pb, 
P,  S,  Bi,  etc.),  and  may  be  carried  out  electrolytically  or  by  a  combined 
gravimetric  and  volumetric  method. 

A.    Electrolytic  Method1 

In  a  small  covered  beaker,  i  gram  of  the  sample  is  dissolved  in  10-12 
c.c.  of  nitric  acid  (D  1-2)  at  a  gentle  heat. 

1.  Determination  of  the  Tin. — The  solution  is  diluted  with  15-20 
c.c.  of  water  and,  if  turbid  owing  to  the  presence  of  metastannic  acid, 
evaporated  to  dryness,  the  residue  being  taken  up  with  a  few  drops  of  nitric 
acid  and  a  little  water.  The  liquid  is  heated  for  some  time  and  the  meta- 
stannic acid  filtered  off,  washed  with  hot  water  acidified  with  nitric  acid, 
ignited  and  weighed  :  SnO2  X  0-7881  =  Sn. 

1  Belasio  and  Mafchionneschi  :    Annali  di  Chimica  applicata,   1914,  I,  p.   127. 


230  COMPLEX  BRASSES 

2.  Determination  of  the  Lead. — The  liquid  freed  from  metastannic 
acid,  or  the  original  solution  if  the  alloy  does  not  contain  tin,  is  evaporated 
on  a  sand-bath  with  5  c.c.  of  dilute  sulphuric  acid  (i  vol.  acid  to  i  vol. 
water)   until  copious  white  fumes  are  emitted.     When  cold,   the  residue 
is  heated  gently  and  stirred  with  50  c.c.  of  water  to  dissolve  the  basic  sul- 
phates of  copper,  zinc,  etc.,  and  the  solution,  after  cooling,  mixed  with 
15  c.c.  of  95%  alcohol.     After  standing  for  1-2  hours,  the  lead  sulphate 
which  separates  is  collected  in  a  Gooch  crucible  and  is  washed  first  with 
a  mixture  of  60  c.c.  water,  10  c.c.  of  alcohol  and  0-5  c.c.  of  sulphuric  acid 
and  then  with  alcohol  until  the  reaction  is  neutral ;  it  is  then  dried,  heated 
and  weighed  :    PbSO4  x  0-6831  =  Pb. 

3.  Determination  of  the  Copper. — -The  filtrate  is  evaporated  almost 
to  dryness  to  eliminate  the  alcohol,  the  residue  being  diluted  with  water  to 
150  c.c.  and  electrolysed  at  the  ordinary  temperature.     Cathode,  Winkler 
electrode  ;    anode,  spiral ;    ND100  =  0-1-0-2   amp.  ;    voltage,    1-7-2  ;    dura- 
tion, 15-16  hours. 

During  the  whole  course  of  the  electrolysis,  the  voltage  at  the  terminals 
should  never  exceed  2,  so  that  it  is  advisable  to  use  a  single  accumulator 
or  a  battery  of  accumulators  joined  in  parallel.  At  the  completion  of  the 
deposition,  the  electrolytic  beaker  is  lowered  slowly  and  the  electrodes 
washed  as  they  emerge.  The  washing  of  the  cathode  is  completed  with 
water,  alcohol  and  ether,  and  the  weight  determined  after  drying  at  70°. 

4.  Separation    of   the    Iron    and    Manganese. — The   spiral   anode, 
which  is  covered  with  a  black  coating  of  manganese  dioxide,  is  immersed 
in  the  liquid  from  which  the  copper  has  been  separated,  this  being  heated 
with  addition  of  3-4  drops  of  hydrogen  peroxide  until  the  manganese  dioxide 
is  completely  dissolved.     The  spiral  is  withdrawn  and  washed,  and  the 
solution  concentrated  to  30-40  c.c.  and  poured,  little  by  little  and  with 
shaking,  into  a  solution  of  10  grams  of  pure  sodium  hydroxide  in  30-40  c.c. 
of  water  contained  in  a  platinum  or  porcelain  dish.     The  iron  and  the  man- 
ganese are  precipitated  as  oxides,  while  the  zinc  and  aluminium  pass  into 
solution  as  sodium  zincate  and  aluminate.     The  liquid  is  heated  to  boiling, 
diluted  with  boiling  water  and  filtered,  the  filtrate  being  collected  in  a  half- 
litre  beaker  containing  about  100  c.c.  of  20%  sulphuric  acid  and  the  filter 
washed  with  hot  water.     The  oxides  separated  are  dissolved  in  a  little 
dilute  sulphuric  acid  containing  a  few  drops  of  hydrogen  peroxide  and  the 
solution  again  poured  into  sodium  hydroxide  solution  of  the  concentration 
mentioned  above,  the  latter  being  heated  to  boiling,  diluted  and  filtered 
and  the  filtrate  collected  in  the  same  half-litre  beaker  as  the  other. 

(a)  DETERMINATION  OF  THE  IRON.  The  ferric  and  manganese  hydroxides 
are  redissolved  in  the  least  possible  quantity  of  10%  sulphuric  acid,  a  few 
drops  of  hydrogen  peroxide  being  added  and  the  solution  heated.  The 
greater  part  of  the  free  acid  is  neutralised  with  ammonia  and  the  solution 
poured  into  a  boiling  solution  of  6-7  grams  of  ammonium  oxalate  in  a  little 
water;  after  addition  of  5-6  c.c.  of  2%  hydrazine  sulphate  solution  and 
dilution  to  about  200  c.c.,  the  liquid  is  electrolysed  to  determine  the  iron 
(see  Ferro-manganese,  Electrolytic  Analysis). 

(6)  DETERMINATION  OF  THE  MANGANESE.    The  liquid  from  which  the 


COMPLEX  BRASSES  231 

iron  has  been  separated  is  concentrated,  with  the  anode  immersed,  to  60— 
70  c.c.  and  the  manganese  determined  as  indicated  in  the  electrolytic  analysis 
of  ferro-manganese. 

5.  Determination   of  the  Zinc. — If  not   already  acid,   the  solution 
containing  the  zinc  and  aluminium  is  acidified  with  dilute  sulphuric  acid, 
evaporated  if  necessary  to  reduce  the  volume  to  200-250  c.c.,  rendered 
alkaline  with  sodium  hydroxide,   acidified  slightly  with  formic  acid  and 
electrolysed  with  rotating  electrodes  to  determine  the  zinc  (see  p.  225). 

6.  Determination  of  the  Aluminium. — The  liquid  from  which  the 
zinc  has  been  removed,  together  with  wash  water,  is  treated  with  ammo- 
nium chloride  and  ammonia  until  the  reaction  is  alkaline,  boiled  for  some 
time  and  the  aluminium  hydroxide  filtered  off,  washed,  dried,  ignited  and 
weighed  :    A12O3  x  0-5303  —  Al. 

7.  Determination  of  the  Phosphorus,  Sulphur,  Bismuth,  Arsenic, 
etc. — See  Ordinary  Brass. 


n.    Combined  Gravimetric  and  Volumetric  Method 

2  grams  of  the  sample  are  dissolved  in  20  c.c.  of  nitric  acid  (I)  1-2)  at 
a  gentle  heat. 

1.  Determination  of  the  Tin,   Lead   and   Copper. — The  liquid  is 
diluted  with  15-20  c.c.  of  water,  and  the  tin,  lead  and  copper  determined 
gravimetrically  as  in  ordinary  brass  (§.t'.). 

2.  Determination  of  the  Iron,  Manganese,  Zinc  and  Aluminium. 
-The  liquid  from  which  the  copper  has  been  separated  as  sulphide  is 

evaporated  to  reduce  its  volume  to  about  200  c.c.  and  to  expel  the  hydrogen 
sulphide,  the  iron  being  oxidised  by  addition  of  a  few  drops  of  hydrogen 
peroxide  and  the  cooled  liquid  made  up  to  300  c.c. 

(a)  VOLUMETRIC  DETERMINATION  OF  THE  IRON.     The  iron  in  50  c.c. 
of  this  solution  is  reduced  with  zinc  amalgam  and  titrated  with  perman- 
ganate in  the  usual  way. 

(b)  VOLUMETRIC    DETERMINATION    OF    THE    MANGANESE.    Two    other 
portions,  each  of  50  c.c.,  are  used  for  the  determination  of  the  manganese 
by  Volhard's  method  (see  Ferro-manganese),  one  for  the  preliminary  test 
and  the  other  for  the  actual  determination. 

(c)  DETERMINATION  OF  THE  ZINC.     A  further  quantity  of  50  c.c.  is 
rendered  alkaline  with  ammonia  and  then  neutralised  with  formic  acid  ; 
for  each  100  c.c.  of  this  solution  4  c.c.  of  50%  formic  acid  are  added  and 
the  zinc  precipitated  by  hydrogen  sulphide.     Ihe  liquid  is  left  overnight 
to  complete  the  precipitation  and  is  then  filtered  through  a  filter-paper  of 
compact  texture  and  washed  with  a  dilute  solution  of  ammonium  formate 
saturated  with  hydrogen  sulphide.1 

When  completely  washed,  the  precipitate  is  dried  and  introduced  into 
a  Rose  crucible,  the  filter  being  burned  in  a  platinum  spiral  and  dropped 
into  the  crucible.  The  precipitate  is  then  mixed  by  means  of  a  platinum 

1  The  ammonium  formate  solution  is  prepared  by  neutralising  a  dilute  solution  of 
formic  acid  (1-2%)  with  ammonia  and  slightly  acidifying  with  formic  acid. 


232  ORDINARY  BRONZES 

wire  with  about  one-third  of  its  weight  of  pure  sulphur  and  heated  in  a 
current  of  hydrogen  to  constant  weight :  ZnS  x  0-6709  --  Zn. 

(d)  DETERMINATION  OF  THE  ALUMINIUM.  The  liquid  from  which  the 
zinc  has  been  removed  is  concentrated  in  a  porcelain  dish  to  small  volume, 
the  iron  being  then  oxidised  with  hydrogen  peroxide  and  the  solution  ren- 
dered alkaline  with  pure  potassium  hydroxide  solution,  boiled,  diluted 
with  boiling  water  and  filtered.  The  filter  is  washed  with  hot  water  and 
the  filtrate  acidified  with  nitric  acid,  rendered  alkaline  with  ammonia  and 
heated  to  boiling  for  a  short  time.  The  precipitated  aluminium  hydroxide 
is  filtered  off,  washed,  dried  to  some  extent,  ignited  in  a  platinum  crucible 
and  weighed  :  A1203  X  0-5303  =  Al. 

3.  Determination  of  the  Phosphorus,  Sulphur,  Arsenic,  Bismuth, 
etc. — See  Ordinary  Brasses. 

*  * 

Of  these  complex  brasses  the  one  most  largely  used  is  the  so-called  "  Delta 
metal,"  of  the  following  mean  composition  :  54-62%  Cu,  38-40%  Zn,  0-5-3% 
Mn,  0-4-1-2%  Fe,  0-02-2-5%  Al,  0-0-5%  pb  and 0-3%  Sn. 


ORDINARY    BRONZES 

Analysis  of  ordinary  bronzes  includes,  besides  determinations  of  the 
constituent  metals  (copper,  tin  and  sometimes  zinc),  also  those  of  the 
extraneous  metals  often  present  in  small  quantities  (lead,  iron,  antimony, 
nickel,  manganese,  phosphorus,  arsenic,  sulphur,  etc.).  Electrolytic  or 
gravimetric  methods  may  be  used. 

A.  Electrolytic    Method 

In  a  covered  beaker,  1-3  grams  of  the  alloy,  as  filings  or  turnings,  are 
treated  in  the  cold  with  15-20  c.c.  of  nitric  acid  (D  =  1-3),  the  liquid  being 
heated  gently  when  the  action  slackens  and  finally  evaporated  almost  to 
dryness. 

1.  Determination  of  the  Tin. — -The  residue  is  taken  up  with  a  few 
drops  of  nitric  acid,  50  c.c.  of  water  being  mixed  in  and  after  about  an  hour 
on  the  water-bath,  the  liquid  filtered  through  a  compact  filter-paper  and 
the  residue  on  the  filter  washed  with  hot  water  acidified  with  nitric  acid 
(i  of  acid  to  100  of  water).  The  filtrate  is  utilised  as  described  in  3  (below). 
The  metastannic  acid  separated  may  be  dried,  ignited  and  weighed,  but  it 
may  contain  various  impurities  (especially  copper  and  phosphorus),  and 
when  an  exact  analysis  is  required  the  following  procedure  is  advisable.1 

1  The  method  of  fusion  with  sulphur  and  sodium  carbonate  indicated  for  the  gravi- 
metric analysis  of  bronzes  (see  p.  234)  may  also  be  used  and,  when  the  antimony  has 
been  removed  by  means  of  hydrogen  sulphide,  the  electrolytic  method  followed. 

Further,  in  absence  of  phosphorus  and  antimony  the  following  simpler  procedure 
may  be  employed.  The  impure  stannic  oxide  is  separated  and  weighed  and  then  dis- 
integrated with  sulphur  and  sodium  carbonate,  the  resulting  fused  mass  being  taken 
up  in  hot  water.  The  copper  sulphide  is  separated  and  determined  and  the  correspond- 
ing weight  of  the  oxide  deducted  from  the  sum,  SnO2  +  CuO.  The  remainder  repre- 
sents pure  stannic  oxide,  which  gives  the  tin  present  in  the  sample.  The  copper  occluded 
in  the  stannic  oxide  is  added  to  the  amount  found  in  the  nitric  acid  solution. 


ORDINARY   BRONZES  233 

The  filter  and  precipitate  are  heated  with  2-3  c.c.  of  10%  sodium 
hydroxide,  and  10-15  c.c.  of  sodium  sulphide  solution  (D  1-225)  m  a  small 
beaker  on  a  water-bath  until  the  metastannic  acid  is  completely  dissolved. 
After  dilution  with  10-15  c.c.  of  water  and  addition  of  a  little  sodium  sul- 
phite dissolved  in  a  little  water  to  reduce  polysulphides,  the  liquid  is  again 
heated  for  a  short  time  and  filtered  by  decantation,  the  filtrate  being  collected 
in  a  f-litre  conical  flask.  The  residue  is  again  treated  with  10-15  c.c.  of 
sodium  sulphide  solution,  heated,  reduced  with  sulphite,  diluted,  filtered  and 
washed  with  hot  water  containing  a  little  sodium  sulphide  until  about 
150-200  c.c.  of  filtrate  are  collected.  The  lead,  copper,  iron,  etc.,  contained 
in  the  metastannic  acid  remain  on  the  filter  as  sulphides.  The  filter  is 
dried  and  then  burnt  in  a  small  dish,  the  residue  being  dissolved  in  a  little 
nitric  acid  (D  1-3)  and  the  solution  obtained  added  to  the  liquid  in  which 
the  copper,  lead,  zinc,  etc.,  are  to  be  determined. 

As  regards  the  determination  of  the  tin  and  antimony,  hydrochloric 
acid  diluted  with  an  equal  volume  of  water  is  added  gradually  and  with 
shaking  (under  a  draught  hood)  to  the  solution  in  sodium  sulphide  until 
the  latter  shows  an  acid  reaction  ;  25-30  c.c.  of  concentrated  hydrochloric 
acid  are  then  added  and  the  liquid  boiled  to  dissolve  the  separated  sul- 
phides, adding,  if  necessary,  a  few  crystals  of  potassium  chlorate. 

When  cold,  the  solution — -which  contains  sulphur  and  is  turbid — is 
rendered  alkaline  with  ammonia  and  then  heated  with  5  grams  of  oxalic 
acid.  When  all  the  tin  hydroxide  precipitated  by  the  addition  of  ammonia 
is  redissolved,  7  grams  of  ammonium  oxalate  are  added,  the  liquid  heated 
to  boiling  and  hydrogen  sulphide  passed  for  about  15  minutes  through 
the  boiling  liquid.  Under  these  conditions,  any  antimony  present  is  alone 
precipitated. 

After  being  allowed  to  cool  somewhat  in  the  current  of  hydrogen  sulphide, 
the  liquid  is  filtered,  the  filtrate  being  collected  in  a  |-litre  beaker  and  the 
washing  effected  with  a  hot  i%  oxalic  acid  solution  saturated  with  hydrogen 
sulphide.  The  antimony  sulphide  precipitate  remaining  on  the  filter  is 
analysed  according  to  2  (below). 

The  filtrate  is  treated  with  30  c.c.  of  cone,  hydrochloric  acid  and  20 
grams  of  ammonium  oxalate,  boiled  for  a  short  time  to  eliminate  hydrogen 
sulphide,  a  few  drops  of  hydrogen  peroxide  added,  heated  again  for  a  short 
time,  allowed  to  cool  to  40-50°,  made  up  to  about  300°  and  electrolysed, 
if  possible  under  a  hood,  to  determine  the  tin  :  coppered  Winkler  cathode  ]  ; 
spiral  anode  ;  ND100  —  i  amp.  ;  voltage  =  3-4  ;  temperature,  40-50°, 
and  duration  (with  o-i-o-3  gram  Sn)  4-5  hours. 

When  the  deposition  of  the  tin  is  complete,  the  electrolytic  beaker  is 
replaced,  without  interrupting  the  current,  by  another  full  of  water  ;  after 
a  time  the  cathode  is  detached,  washed  with  an  abundant  supply  of  water 
and  then  with  alcohol  and  ether,  and  dried  at  70°. 

1  To  prevent  attack  of  the  copper  coating  by  the  acid  solution  while  the  arrange- 
ments for  the  electrolysis  are  being  made,  the  electrodes  should  be  fixed  on  supports 
at  the  required  height  and  connected  with  the  source  of  current,  the  beaker  being  then 
raised  to  immerse  them.  In  this  way  the  current  begins  to  flow  immediately  the  elec- 
trodes dip  into  the  liquid  and  so  prevents  attack  of  the  copper. 


234  ORDINARY   BRONZES 

2.  Determination    of   the    Antimony.— -The     filter-paper    with     the 
antimony  sulphide  is  heated  in  a  beaker  with  4  c.c.  of  50%  sodium  hydroxide 
solution  and  20-30  c.c.  of  sodium  sulphide  (D  =  1-225)  until  the  antimony 
sulphide  is  completely  dissolved.     After  some  time  the  liquid  is  filtered 
directly  into  the  Classen  dish,  the  vessel  and  filter  being  washed  with  50-60 
c.c.  of  sodium  sulphide.     The  filtrate  is  treated  with  5-6  grams  of  potassium 
cyanide  to  decolorise  the  sodium  sulphide  and  to  prevent  formation  of 
polysulphides  during  the  electrolysis,  which  is  carried  out  at  the  ordinary 
temperature.     Cathode,   Classen  capsule ;    anode,  disc  or    spiral  ;    ND100 
=  0-15-0-18    arrp.  ;     voltage  =  1-1-2  ;     duration    (0-1-0-15    gram    Sb)  - 
15-18  hours. 

When  the  antimony  is  all  deposited,  the  anode  is  withdrawn,  the  cap- 
sule rapidly  emptied,  washed  with  water,  alcohol  and  ether,  and  dried  at 
70°. 

The  antimony  is  afterwards  removed  from  the  dish  by  treatment  with 
nitric  acid  (D  1-2)  containing  a  little  tartaric  acid  in  solution. 

3.  Determination  of  the  Copper,  Lead,  Iron  and  Zinc. — The  liquid 
from  which  the  metastannic  acid  was  separated  (see  i)  is  acidified  with 
15-20  c.c.  of  nitric  acid  (D  1-2),  mixed  with  the  nitric  acid  solution  of  the 
oxides  extracted  from  the  metastannic  acid  and  the  whole  treated  as  in  the 
analysis  of  ordinary  brass  (q.v.}. 

4.  Determination  of  the  Nickel. — See  Nickel  Bronzes. 

5.  Determination  of  the  Manganese. — See  Manganese  Bronzes. 

6.  Determination   of   the   Silver. — -5-10   grams   of   the   sample   arc 
treated  with  nitric  acid  and  freed  from  metastannic  acid  in  the  ordinary 
way.     In  the  filtrate  the  silver  is  precipitated  with  hydrochloric  acid  by 
the  procedure  followed  for  the  determination  of  silver  in  copper.1 

7.  Determination  of  the  Phosphorus. — See  Phosphor  Bronzes. 

8.  Determination  of  the  Arsenic. — See  Copper. 

9.  Determination  of    the  Sulphur.  —2    grams    of    the    sample    are 
treated  with  nitric  acid  and  the  stannic  acid  separated  as  usual.     From 
the  filtrate  the  copper  is  eliminated  by  electrolysis  in  nitric  acid  solution, 
the  residual  liquid  being  evaporated  to  dryness  and  the  sulphur  then  deter- 
mined as  in  copper  (q.v.}. 

B.     Gravimetric  Method 

1.  Determination  of  the  Tin.- — In  a  covered  beaker,  1-2  grams  of 
the  alloy  as  filings  are  treated  with  15-20  c.c.  of  nitric  acid  (D  1-3),  the 
metastannic  acid  being  separated,  washed,  ignited  in  a  porcelain  crucible 
and  weighed  :  SnO2  x  0-7881  =  Sn.  The  filtrate  is  treated  as  in  3. 

The  stannic  oxide  thus  weighed  is  always  impure  and,  where  an  exact 
determination  is  necessary,  it  is  powdered  in  an  agate  mortar,  mixed  with 
6  parts  of  a  mixture  of  ignited  sodium  carbonate  and  sulphur  in  equal  pro- 
portions, and  heated  at  a  gentle  heat  with  the  crucible  covered  until  all  the 
sulphur  is  expelled. 

1  Since  silver  is  deposited  with  the  copper  on  the  cathode,  the  data  relating  to 
copper  must  be  corrected  by  the  amount  found. 


ORDINARY   BRONZES  235 

When  cold,  the  mass  is  taken  up  in  hot  water  and  the  brown  solution 
heated  with  sodium  sulphite  until  it  becomes  pale  yellow.1  The  liquid  is 
then  filtered  and,  the  precipitate  washed  with  water  containing  a  little  sodium 
sulphide  and  then  with  hydrogen  sulphide  solution  ;  the  filter  is  burnt  in 
a  small  dish  and  the  residue  dissolved  in  a  little  nitric  acid  and  the  solution 
added  to  the  filtrate  from  the  metastannic  acid  containing  the  bulk  of  the 
copper,  lead,  zinc,  etc.,  dealt  with  as  in  3. 

The  solution  contains  all  the  tin  and  antimony  present  as  sulpho -salts. 
This  liquid  is  treated  in  a  | -litre  conical  flask  with  6  grams  of  caustic  potash, 
3  grams  of  tartaric  acid  and,  slowly  and,  if  necessary,  with  cooling,  with 
sufficient  30%  hydrogen  peroxide  to  give  complete  decoloration,  that  is, 
to  convert  the  sulphide  completely  into  sulphate.  The  liquid  is  boiled 
for  some  time  to  expel  excess  of  hydrogen  peroxide,  allowed  to  cool,  neu- 
tralised carefully  with  oxalic  acid,  treated  with  an  excess  of  3-5  grams  of 
oxalic  acid,  diluted  to  250-300  c.c.,  heated  to  boiling,  and  a  moderate  current 
of  hydrogen  sulphide  passed  through  the  boiling  liquid  for  about  an  hour. 
The  liquid  is  then  allowed  to  cool  somewhat  and  any  precipitated  antimony 
sulphide  collected  in  a  tared  Gooch  crucible,  and  washed  first  with  i% 
oxalic  acid  solution  saturated  with  hydrogen  sulphide  and  afterwards  with 
very  dilute  hot  acetic  acid  saturated  with  hydrogen  sulphide. 

To  determine  the  tin,  the  filtrate  is  rendered  slightly  alkaline  with 
ammonia,  acidified  with  acetic  acid,  and  the  tin  precipitated  with  hydrogen 
sulphide.  After  the  precipitation,  the  liquid  is  left  at  rest  for  about  half 
an  hour  on  the  water-bath  to  facilitate  the  separation  of  the  precipitate, 
and  finally  filtered,  being  washed  with  hydrogen  sulphide  solution  contain- 
ing a  little  ammonium  sulphate  in  solution.  The  tin  sulphide  thus  obtained 
is  dried  at  120°,  converted  by  ignition  into  oxide  and  weighed. 

2.  Determination  of  the  Antimony. — The  antimony  sulphide  in  the 
Gooch  crucible  is  converted  by  any  of  the  known  methods  2  into  the  tri- 
sulphide  and  weighed  directly  :    Sb2S3  x  0-7142  =  Sb. 

3.  Determination    of   the   Lead,    Copper,    Iron,   Zinc,    etc. — The 
filtrate  obtained  after  the  action  of  nitric  acid  on  the  alloy,  together  with 
the  nitric  acid  solution  of  the  metals  extracted  from  the  metastannic  acid, 
is  treated  with  2-3  c.c.  of  cone,  sulphuric  acid,  the  further  procedure  being 
as  given  for  the  analysis  of  ordinary  brasses  (q.v.). 

4.  Determination  of  the  Manganese,  Silver,  Phosphorus,  Arsenic 
and  Sulphur. — See  preceding  method. 

* 
*  * 

The  compositions  of  bronzes  vary  widely  with  the  requirements  as  regards 
hardness,  elasticity,  colour,  sonority,  etc. 

Bronzes  for  machine  gearing  and  the  old,  highly  elastic,  tenacious  and 
resistant  bronzes  for  cannon  contained  on  the  average  90  %  Cu  and  10  %  Sn  ;  those 
for  cocks,  cast  machine  parts,  etc.,  87%  Cu,  13%  Sn,  and  often  small  amounts  of 
zinc  ;  those  for  bushes  and  collars,  82-84%  Cu  and  16-18%  Sn.  Bronzes  for 

1  If  the  residue  insoluble  in  water  has  a  sandy  aspect,  the  disaggegration  is  incom- 
plete.    In  such  case  the  filter  is   dried  and   burnt  and   the   residue  again   fused  with 
sulphur  and  sodium  carbonate. 

2  See  Tread  well  :    Analytical  Chemistry,  Vol.  II. 


236  SPECIAL  BRONZES 

bells,  very  hard  and  sonorous  but  brittle,  contain  usually  75-80%  Cu,  20-25% 
Sn,  and  sometimes  small  quantities  of  zinc,  lead,  silver,  etc.  Silver-coloured 
bronzes  for  small,  highly  sonorous  bells  contain  40-42%  Cu  and  58-60%  Sn. 
Statuary  bronze  contains  also  considerable  proportions  of  zinc  (78-90%  Cu, 
2-4%  Sn,  10-18%  Zn). 

As  a  rule  commercial  bronzes,  besides  copper  and  tin,  contain  small  quan- 
tities of  other  elements  (especially  zinc,  iron,  manganese,  nickel,  lead,  antimony, 
phosphorus,  arsenic,  sulphur,  etc.),  which,  even  in  small  proportions,  may  pro- 
foundly modify  the  properties  of  the  alloy  (see  Special  Bronzes)  ;  so  much  is  this 
the  case  that  it  is  not  always  easy  to  decide  if  these  elements  are  impurities  of 
the  raw  materials  used  or  if  they  have  been  added  to  obtain  certain  specific 
properties. 

Zinc  in  small  quantities  (0-5-2%)  renders  bronze  more  easy  to  cast  and 
increases  its  strength  and  elasticity  ;  if,  however,  the  proportion  is  slightly 
greater  than  2%,  the  bronze  loses  its  hardness  and  strength  and  assumes  pro- 
perties approximating  to  those  of  the  brasses. 

The  presence  of  lead  is  especially  harmful  in  bronzes  for  machines  and  tools, 
even  if  it  is  only  slightly  greater  than  0-5%,  since  it  diminishes  the  homogeneity 
of  the  alloy.  In  proportions  not  exceeding  1-5%,  iron  exerts  an  action  analogous 
to  that  of  zinc  and  increases  considerably  the  hardness  of  the  bronze.  Arsenic, 
antimony,  bismuth  and  sulphur  are  highly  injurious,  and  even  in  the  proportion 
of  0-1%  render  the  bronze  brittle.  Nickel,  manganese  and  phosphorus  improve 
the  quality  of  the  alloy  and  are  often  added  (see  Nickel-bronze,  Manganese- 
bronze,  Phosphor-bronze,  etc.). 


SPECIAL    BRONZES 

These  are  copper-tin  alloys  containing  anothe;  element  added  with  a 
definite  object.  Those  in  more  common  use  are  :  phosphor-,  silicon-, 
manganese-,  lead-,  nickel-,  lead-nickel-  and  aluminium-bronzes. 

Phosphor  -bronzes 

Phosphor-bronzes  are  so  called  because  during  their  preparation  a  small 
quantity  of  phosphorus  is  added  as  phosphor-copper  or  phosphor-tin  with 
a  view  to  reduce  the  metallic  oxides  contained  in  the  metal  and,  therefore, 
to  impart  greater  hardness,  strength,  elasticity,  etc.  The  attempt  is  usually 
made  to  add  the  quantity  of  phosphorus  just  necessary  for  the  deoxidation 
(there  may,  therefore,  be  phosphor-bronzes  free  from  phosphorus),  or  at 
most  only  a  slight  excess,  so  that  only  a  very  small  amount  passes  into  the 
alloy.  The  analysis  includes  determinations  of  the  usual  constituents 
and  impurities  and  also  that  of  phosphorus. 

1.  Determination  of  the  Phosphorus. — (a)  IN  ABSENCE  OF  ARSENIC. 
2  grams  of  the  sample  are  dissolved  in  aqua  regia  or  in  hydrochloric 
acid  and  potassium  chlorate,  the  solution  being  repeatedly  evaporated  to 
dryness  with  hydrochloric  acid,  the  residue  then  dissolved  in  dilute  hydro- 
chloric acid  and  water  and  the  phosphoric  acid  precipitated  with  ammonium 
molybdate  as  in  the  determination  of  phosphorus  in  iron  (see  p.  173). 

(fy  IN  PRESENCE  OF  ARSENIC.  After  the  repeated  evaporation  with 
hydrochloric  acid,  the  residue  is  taken  up  twice  in  hydrobromic  acid  and 
evaporated  to  dryness  each  time.  The  residue  is  then  taken  up  in  cone, 
hydrochloric  acid,  evaporated  to  dryness,  the  residue  dissolved  in  dilute 


SPECIAL   BRONZES  237 

hydrochloric  acid  and  the  phosphoric  acid  precipitated  in  the  usual  way 
(see  Determination  of  Phosphorus  in  Iron  in  presence  of  Arsenic). 

2.  Determination  of  Tin,  Copper,  Zinc,  etc. — See  Ordinary  Bronzes.1 


* 
*  * 


In  some  bronzes  for  bushes,  pistons,  etc.,  subject  to  attrition,  quantities  of 
phosphorus  varying  from  0-25  to  2-5%  are  sometimes  present  with  a  view  to 
obtaining  quite  special  effects.  In  ordinary  phosphor-bronzes  smaller  quan- 
tities are  found  (less  than  0-25%). 


Silicon  -bronzes 

These  are  used  especially  for  telegraph  and  telephone  wires,  as  they 
have  high  electrical  conductivity  and  resistance  to  tension.  Their  analysis 
includes  : 

1.  Determination  of  Silicon. — 2-10  grams  of  the  sample,  according 
to  the  supposed  silicon  content,  are  treated  with  aqua  regia  (3  parts  of 
hydrochloric  acid  and  I  part  of  nitric  acid),  the  solution  being  evaporated 
to  dryness,  the  residue  taken  up  twice  with  about  15  c.c^  of  concentrated 
hydrochloric  acid  and  evaporated,  and  the  residue  heated  in  an  oven  at 
135°  to  render  the  silica  completely  insoluble.     The  residue  is  treated  with 
hydrochloric  acid,  the  subsequent  procedure  being  as  in  the  determination 
of  silicon  in  iron.     In  the  present  case  also  the  purity  of  the  silica  must  be 
investigated  by  treatment  with  sulphuric  and  hydrofluoric  acids. 

2.  Determination  of  the  Tin,  Iron,  Zinc,  Nickel,   Phosphorus, 
Sulphur,  etc. — As  with  ordinary  bronzes2  (q.v.}. 


Silicon-bronzes,  besides  a  little  tin  and  often  a  little  zinc,  contain  very  small 
quantities  of  silicon  (0-05-1%)  introduced  in  the  form  of  silicon-copper  as  a 
deoxidiser.  According  to  Hampe  the  best  bronzes  for  telegraph  and  telephone 
wires  have  the  following  percentage  compositions  : 

TABLE    XXIV 
Compositions  of  Silicon -bronzes 

Cu  Sn  Si  Fe  V.n 

For  telephone  wires    .      97-12          1-14         0-05         trace         1-12 
For  telegraph  wires    .     99-94         0-03         0-03         trace 

Lead -bronzes 

Lead-bronzes,  also  called  American  bronzes  owing  to  their  widespread 
use  in  America,  besides  copper  and  tin  contain  considerable  quantities  of 
lead  and  sometimes  phosphorus,  and  are  used  for  bearings  and  parts  of 
machines  subject  to  friction,  the  lead  increasing  largely  the  plasticity  of  the 
alloy.  Their  analysis  includes  : 

1.  Determination  of  the  Tin,  Lead,  Copper,  Iron,  Zinc,  etc. — 

1  The  presence  of  phosphorus  in  the  metastannic  acid  separating  to  be  borne  in  mind. 

2  The  presence  of  silica  in  the  metastannic  acid  separating  to  be  borne  in  mind. 


238 


SPECIAL  BRONZES 


i  gram  of  the  alloy  is  dissolved  in  15-20  c.c.  of  nitric  acid  (D  1-3),  the 
solution  evaporated  to  dryness,  the  residue  taken  up  with  a  few  drops  of 
nitric  acid  and  hot  water,  and  the  separate  determinations  carried  out  as 
with  ordinary  bronzes  (q.v.). 

2.  Determination  of  the  Phosphorus. — i  gram  of  the  sample,  as 
filings,  is  dissolved  in  aqua  regia,  evaporated  to  dryness,  repeatedly  taken 
up  with  hydrochloric  acid  and  evaporated  to  dryness,  and  the  residue  dis- 
solved in  dilute  hydrochloric  acid  and  hot  water  (400-500  c.c.)  and  the  hot 
solution  treated  with  hydrogen  sulphide.  The  precipitate  is  washed  on 
a  Gooch  crucible  with  hot  water  saturated  with  hydrogen  sulphide  and 
acidified  with  hydrochloric  acid  and  the  filtrate  evaporated  to  dryness  with 
nitric  acid. 

The  residue  is  dissolved  in  a  little  nitric  acid  and  the  phosphoric  acid 
precipitated  with  ammonium  molybdate  as  in  the  determination  of  phos- 
phorus in  iron. 

* 

*  * 

The  following  table  gives  the  compositions  of  various  types  of  commercial 
lead-bronzes  (Guillet,  Muspratt,  Ledebur)  : 

TABLE   XXV 
Composition  of  Lead -bronzes 


Cti 

Sn 

Pb 

Zn 

P 

I-e           Sb 

Ni 

As 

I      ... 

8470 

10-05 

4-co 

0-46 

c-ii 

_ 

0-14 

_ 

•2       ... 

84-00 

3-00 

4-56 

8-50 

— 

—           — 

—  .           — 

3      •      •      • 

83-85 

8-32 

7-36 

0-13       0-31 

trace 

— 

0-04 

41    •      •      • 

7970 

10-00 

9-50 

— 

c-8o 

—         — 

—           — 

5      •      •      • 

73-50 

9-50 

9-50 

9-50 

— 

0-50 

— 

.  —  . 

6      ... 

78-01 

10-36 

10-45 

0-57      o-cc) 

1 

0-26 

Manganese  -bronzes 

Manganese-bronzes,  which  should  not  be  confused  with  manganese- 
brasses — often  improperly  given  this  name — or  manganese-copper  alloys, 
are  composed  essentially  of  copper  and  tin  with  small  proportions  of  man- 
ganese (1-3%).  Their  analysis  comprises  : 

1.  Determination  of  the  Tin. — As  in  ordinary  bronzes. 

2.  Determination   of  the   Lead,   Copper,   Iron,   Manganese   and 
Zinc. — The  liquid  from  which  the  metastannic  acid  has  been  separated, 
together  with  the  solution  of  the  metals  occluded  in  the  metastannic  acid, 
is  evaporated  with  sulphuric  acid  and  the  separate  determinations  carried 
out  as  with  complex  brasses. 

3.  Determination  of  the  Phosphorus,  Arsenic  and  Sulphur. — See 
Ordinary  Bronzes. 

1  Type  adopted  by  the  Italian  State  Railways. 


SPECIAL   BRONZES 


239 


The  compositions  of  the  commoner  commercial  types  of  manganese-bronzes 
are  as  follows   (Guillet)  : 

TABLE   XXVI 
Composition  of  Manganese -bronzes 


Cu 

Sn 

Zn.                       Mn 

P 

j 

92 

8 

I 

_ 

2 

84                    14 

2 

— 

3      •      •      • 

82                    15 

3 

— 

4      ... 

92 

8 

3                     0-5                trace 

Nickel -bronzes 

The  addition  of  small  proportions  of  nickel  to  bronzes  increases  the 
hardness  and  lustre  and  imparts  a  pleasing,  golden  colour. 
Their  analysis  includes  : 

1.  Determination  of  the  Tin. — 2  grams  of   the  sample  are  treated 
in  a  covered,  tall,  narrow  beaker  with  20  c.c.  of  nitric  acid  (D  1-2),  the 
solution  being  evaporated  to  dryness,  taken  up  with  a  few  drops  of  nitric 
acid  and  hot  water  and  heated  for  a  short  time  on  the  water-bath.     The 
metastannic  acid  is  collected  on  a  close  filter-paper  and,  being    in  small 
quantity,  may  be  weighed  directly  after  washing  with  hot  water  acidified 
with  nitric  acid,  drying  and  calcining. 

2.  Determination  of  the  Lead,  Copper,  Iron,  Nickel  and  Zinc.— 
These  elements  are  determined  in  the  liquid  freed  from  metastannic  acid 
by  the  methods  given  for  the  analysis  of  argentan  (see  later). 

3.  Determination  of  the  Phosphorus,  Arsenic  and  Sulphur. — See 
Ordinary  Bronzes. 


Nickel-bronzes  have  the  following  mean  composition  : 
Sn,  6-7°;   Zn,  2-3%  Ni,  and  0-1-0-3%  Pb. 


3-89%  Cu,  2-3% 


Lead -nickel -bronzes 

These  are  very  soft  and  are  also  called  plastic  bronzes  and  serve  mostly 
as  antifriction  metals.     Their  analysis  comprises  : 

1.  Determination   of  the   Tin. — 2  grams  of  the  alloy  are  dissolved 
in  a  covered,  tall,  narrow  beaker  with  20  c.c.  of  nitric  acid  (D  1-3),  the  solu- 
tion evaporated  to  dryness,  and  the  analysis  continued  as  with  ordinary 
bronzes  (q.v.). 

2.  Determination  of  "he  Lead. — The  solution  freed  from  metastannic 
acid  and  the  solution  of  the  oxides  of  copper  and  lead  retained  by  the  meta- 
stannic acid  are  evaporated  together  to  a  small  volume  and  then  heated 


240  SPECIAL  BRONZES 

on  a  sand-bath  with  3-4  c.c.  of  cone,  sulphuric  acid  until  white  fumes  of 
sulphuric  acid  appear.  The  lead  is  determined  as  sulphate  in  the  way 
given  for  the  gravimetric  analysis  of  ordinary  brasses. 

3.  Determination   of   the   Copper,   Iron,   Nickel    and   Zinc. — (a) 
ELECTROLYTIC  ALLY.     The  liquid  freed  from  lead  is  evaporated  until  the 
alcohol  is  expelled  and  the  residual  liquid  mixed  with  20  c.c.  of  nitric  acid 
and  electrolysed  as  in  the  case  of  argentan. 

(b)  GRAVIMETRICALLY.  The  liquid  freed  from  lead  is  evaporated  to 
eliminate  the  alcohol,  mixed  with  200-250  c.c.  of  water,  heated  to  boiling 
and  the  copper  precipitated  with  hydrogen  sulphide,  the  subsequent  pro- 
cedure being  that  described  for  the  gravimetric  analysis  of  argentan. 

4.  Determination   of  the   Phosphorus,   Arsenic   and   Sulphur. — 
See  Ordinary  Bronzes. 


*** 


Lead-nickel-bronzes  have  the  following  mean  composition  :    64%  Cu,  30% 
Pb,  5%  Sn,  and   i%  Ni. 


Aluminium  -bronzes 

Aluminium-bronzes  have  a  fine,  golden-yellow  colour  and  are  used  for 
making  vases,  ornamental  articles,  etc.  They  consist  essentially  of  copper 
and  aluminium  (3-10%)  and  often  contain  small  quantities  of  silicon  and 
iron.  Their  analysis  includes  : 

1.  Determination    of   the    Silicon. — i  gram  of   the  alloy  is   heated 
gently  with  10  c.c.  of  nitric  acid  (D  1-2)  and  the  solution  evaporated  with 
10  c.c.  of  50%  sulphuric  acid  until  white  fumes  of  sulphuric  acid  appear. 
The  residual  liquid  is  mixed  with  30  c.c.  of  water,  heated  for  some  time  and, 
when  cold,  filtered  through  a  small  filter ;   the  residue  of  more  or  less  pure 
silica  is  washed,  dried,  calcined  in  a  platinum  crucible  and  weighed.     It  is 
then  treated  with  hydrofluoric  acid,  etc.,  as  in  the  determination  of  silicon 
in  iron. 

2.  Determination  of  the  Copper. — The  filtrate  is  treated  with  4-5 
c.c.  of  nitric  acid,  diluted  to  about  150  c.c.  and  subjected  to  electrolysis 
(see  Electrolytic  Determination  of  Copper  in  Ordinary  Brasses). 

3.  Determination    of   the    Iron    and    Aluminium. — After   removal 
of  the  copper,  the  liquid  is  rendered  alkaline  with  ammonia,  boiled  for  some 
time  and  the  precipitated  aluminium  and  ferric  hydroxides  filtered  off, 
washed,  calcined  and  weighed.     The  oxides  are  then  fused  with  potassium 
bisulphate,  the  residue  taken  up  in  dilute  sulphuric  acid  and  the  iron  in 
the  solution  determined  electrolytically  or  volumetrically.     The  iron  and 
aluminium  are  thus  obtained  separately. 

*** 

The  compositions  of  the  more  important  industrial  types  of  alumiuium- 
bronzes  are  as  follows  (Guillet)  : 


ZINC  AND   ITS  ALLOYS 

TABLE   XXVII 
Composition  of  Aluminium -bronzes 


241 


Cu 

Al 

Si 

Fe 

I    

02—06 

4-8 

•2.  (for  automobiles) 

94-9 

4'7 

0-41 

O'lO 

3                 do.                  .      . 

95'4 

4-0 

°'33 

O-I2 

4                 do. 

97-0 

2-7 

0-19 

O'2O 

ZINC    AND   ITS    ALLOYS 

In  this  place  zinc  as  such  will  be  treated  and  methods  described  for 
determining  its  common  impurities  ;  technical  tests  for  zinc  dust  are  also 
given.  As  regards  the  numerous  alloys  in  which  zinc  occurs,  those  with 
copper  are  dealt  with  under  copper  and  its  alloys  and  those  with  nickel  under 
nickel  and  its  alloys. 


ZINC 

The  extraneous  elements  commonly  found  in  commercial  zinc  are  lead, 
iron  and  cadmium.  Small  quantities  of  arsenic,  antimony  and  sulphur 
are  also  often  found  and  in  remelted  zinc  also  tin,  but  only  rarely  are  traces 
of  carbon,  silicon,  phosphorus,  copper,  nickel,  cobalt,  etc.,  found. 

The  essential  determinations  to  be  made  on  commercial  zinc  are  those 
of  lead,  iron  and  cadmium.  It  may  sometimes  be  of  interest  to  estimate 
the  arsenic,  antimony  and  sulphur,  but  as  a  rule  it  is  sufficient  to  test  quali- 
tatively for  the  other  elements. 

1.  Determination  of  the  Lead,  Iron  and  Cadmium  (according  to 
Mylius  and  Fromm  l}. — -To  100  grams  of  the  sample  and  200  c.c.  of  water, 
in  a  flask  holding  about  2  litres,  nitric  acid  is  added  gradually  until,  with 
gentle  heating,  the  metal  is  completely  attacked. 

The  solution  obtained  is  then  treated  with  ammonia  until  the  zinc 
hydroxide  at  first  separating  redissolves,  and  then  diluted  to  about  two  litres, 
very  dilute  ammonium  sulphide  being  next  added  in  small  quantities  and 
with  stirring  until  the  lead,  iron  and  cadmium  arc  completely  precipitated 
and  zinc  sulphide  begins  to  appear.2  The  liquid  is  kept  at  80°  for  a  short 
time  to  facilitate  separation  of  the  precipitate,  which  consists  of  lead,  cad- 
mium, iron,  etc.,  sulphides  mixed  with  zinc  sulphide,  and  is  filtered  off  when 
the  supernatant  solution  becomes  clear.  The  precipitate  is  treated  on  the 
filter  with  hot,  dilute  hydrochloric  acid,3  which  dissolves  lead,  cadmium 

1  Zeitschr.  analyt.  Chem.,   1897,  p.  37. 

2  A  small  portion  of  the  liquid,  filtered  and  treated  with  ammonium  sulphide,  should 
yield  a  distinctly  white  precipitate. 

»  aN-Hydrochloric  acid  (20  c.c.  of  cone.  HC1  made  up  to  too  c.c.).  It  is  advisable 
to  place  the  acid  in  a  wash-bottle  and  to  wash  with  it  also  the  flask  in  which  the  precipi- 
tation took  place.  About  150-200  c.c.'  to  be  used  in  all. 

A.C.  16 


242  ZINC 

and  iron  sulphides,  these  being  estimated  as  under  a,  b  and  c  (below)  ;  the 
copper  and  silver  sulphides,  which  remain  undissolved,  may  be  dissolved 
in  nitric  acid  and  estimated  by  the  ordinary  methods. 

(a)  DETERMINATION  OF  THE  LEAD.     The  hydrochloric  acid  solution  is 
evaporated  in  presence  of  sulphuric  acid  and  heated  until  white  fumes 
appear,  the  cold  residue  being  taken  up  in  water  and  alcohol  added  ;  the 
subsequent    procedure    is  as  'in  the    gravimetric    determination    of    lead 
in  brass  (see  p.  226). 

(b)  DETERMINATION   OF  THE   CADMIUM.     The   liquid   freed   from   lead 
sulphate  is  evaporated  until  the  alcohol  is  expelled,  neutralised  exactly 
with  ammonia,  treated  for  every  100  c.c.  of  liquid  with  10  c.c.  of  25% 
hydrochloric  acid  (D  1-125)  and  then  with  hydrogen  sulphide.     The  pre- 
cipitate is  filtered  off,  washed  with  saturated  hydrogen  sulphide  solution 
and  dissolved  in  nitric  acid   (D  1-2),  the  solution  being  evaporated  in  a 
tared  platinum  crucible  in  presence  of  a  slight  excess  of  sulphuric  acid, 
the  excess  of  the  latter  being  eliminated  and  the  residue  heated  gently  and 
weighed  :    CdSO4  X  0-5392  =  Cd. 

(c)  DETERMINATION  OF  THE  IRON.     The  excess  of  hydrogen  sulphide 
is  eliminated  from  the  filtrate  from  the  cadmium  sulphide,  the  iron  being 
oxidised  by  a  few  drops  of  hydrogen  peroxide  or  bromine  water,  and  ammonia 
added  until  the  reaction  is  alkaline.     After  a  short  rest  on  a  water-bath, 
the  precipitated  ferric  hydroxide  is  filtered  and  washed.     To  free  the  pre- 
cipitate from  all  traces  of  zinc,  it  is  redissolved  in  dilute  hydrochloric  acid, 
again  precipitated  with  ammonia,  filtered  off,  washed  with  slightly  ammo- 
niacal  water,  dried,  ignited  and  weighed  :    Fe203  X  0-6994  —  Fe. 

2.  Determination  of  the  Sulphur,  Antimony  and  Arsenic  (accord- 
ing to  Gunther  !).• — -100  grams  of  the  sample  are  placed  in  a  large  flask 
furnished  with  a  delivery  tube  and  with  a  tapped  funnel,  the  stem  of 
which,  bent  up  at  the  end,  reaches  almost  to  the  bottom  of  the  vessel.  The 
air  is  expelled  by  means  of  pure  hydrogen  washed  by  passing  it  through 
silver  nitrate  solution  and  the  delivery  tube  connected  with  two  washing 
bottles,  the  first  containing  a  solution  of  cadmium  cyanide  in  potassium 
cyanide  and  the  second  silver  nitrate  solution,  pure  dilute  sulphuric  acid 
being  then  gradually  introduced  by  means  of  the  tapped  funnel  until  the 
metal  dissolves  completely.  When  evolution  of  gas  ceases,  a  moderate 
current  of  hydrogen  is  passed  through  the  apparatus  to  displace  the  gaseous 
products  of  the  reaction.  The  first  washing  bottle  retains  the  sulphur  as 
cadmium  sulphide,  which  is  filtered  off  and  converted  into  sulphate  (see  i) 
and  weighed. 

In  the  second  bottle,  if  hydrogen  arsenide  and  antimonide  are  present, 
metallic  silver  and  silver  antimonide  2  separate.  The  precipitate  is  filtered 
off,  washed  and  dissolved  in  nitric  and  tartaric  acids,  the  silver  being  then 
precipitated  as  chloride,  which  is  filtered  off,  washed,  dried  and  weighed. 
In  the  filtrate,  the  greater  part  of  the  acidity  is  neutralised  with  ammonia 

1  Zeitschr.  analyt.  Chem.,   1881,  XX,  p.  503. 

2  The  reaction  occurs  according  to  the  equations  : 

SbH3  +  3AgN03     +  aq.        =  Ag3Sb  +  3HNO3  +  aq. 
2AsH3  +  izAgNOj,  +  3H20  =  j2Ag    +  jaHNO,  +  As2O3. 


ZINC   DUST 


243 


and  the  antimony  precipitated  with  hydrogen  sulphide  and  weighed  as 
trisulphide  or  oxide.  The  silver  corresponding  with  the  amount  of  anti- 
mony found  (Ag3Sb)  is  deducted  from  the  total  silver  found,  and  the  arsenic 
corresponding  with  the  remainder  calculated  :  2As  =  i2Ag. 


Refined  zinc  of  good  quality  should  not  contain  more  than  1-5%  of  ex- 
traneous elements  (Pb,  Fe,  Cd,  Cu,  etc.)  and  not  more  than  0-1%  of  As,  Sb  and 
S  together.  The  presence  of  lead  in  small  quantities  (0-2-1-5%)  in  zinc  is  not 
very  harmful,  but  with  more  than  2-3%  of  lead,  zinc  becomes  brittle  and  diffi- 
cult to  roll  into  sheets.  Iron  rarely  occurs  in  greater  proportion  than  0-2% 
and  in  such  amount  is  not  injurious,  but  in  greater  quantity  it  renders  the  metal 
hard  and  brittle.  Cadmium  also  is  always  present  in  small  proportion  (o-oi- 
0-1%)  and  is  not  deleterious  unless  the  zinc  is  to  be  used  for  making  zinc  white. 
Tin  is  found  only  in  remelted  zinc.  Arsenic,  antimony  and  sulphur  are  usually 
found  in  traces,  but  if  together  they  exceed  0-1%  the  metal  is  very  brittle  ;  a 
similar  effect  is  exerted  by  copper  to  the  extent  of  0-5%.  Carbon  and  silicon, 
which  may  sometimes  be  present  in  small  proportions,  have  no  appreciable 
injurious  action. 

The  compositions  of  various  refined  zincs  of  commerce  are  as  follows  (Schnabel, 
Nissenson,  Hollard)  : 

TABLE   XXVIII 
Composition  of  Zincs 


Source. 

Zn' 

Pb 

Fe 

Cd 

Ag 

Cu 

Sb 

As 

S 

Si 

C 

Upper  Silesia  |  j     ' 

98-782 
98-930 

1-118 

I-OOO 

0-024 
0-030 

0-012 
O'OlS 

— 

- 

O-O22 

- 

- 

- 

- 

Pulaski  (U.S.)  Bertha 

Spelter     .... 

99-981 

— 

0-019 

— 

— 



— 

— 

—  • 



.            (  Font  d'Art 

98-904 

1-070 

0-016      o-oio 

—     |     —  • 



— 

— 

— 



-  V.B.M. 

Montague  (     extra 

99-757 

0-192 

0-049       trace 

O-OO2             

— 

— 

— 



1  I     . 

98-752 

1-1524 

0-0073 

0-0705 

0-0002     trace     0-0020 

0-0015 

0-0035 

0-0022* 

0-0075 

!  II    .       .      . 

99-868 

0-1094 

0-0065 

0-0075 

trace     0-0005 

0-0018 

0-0005 

0-0005 

0-0035 

0-0006 

ZINC    DUST 

Commercial  zinc  dust  constitutes  a  mixture  of  very  finely  divided  zinc 
mixed  with  zinc  oxide  and  variable  proportions  of  cadmium,  iron,  lead, 
arsenic,  carbon,  etc.,  and  is  used  as  a  reducing  agent.  It  is  usual  to  deter- 
mine its  reducing  power  towards  solutions  of  potassium  dichromate  or 
ferric  salts  ;  in  some  cases,  however,  the  volume  of  hydrogen  obtained 
under  the  action  of  dilute  hydrochloric  acid  is  measured,  the  quantity  of 
zinc  present  and  hence  the  commercial  value  being  deduced  therefrom. 

1.  Determination  of  the  Reducing  Power. — Reagents:  N/2-potas- 
sium  dichromate  (24-54  grams  per  litre)  and  N/2-thiosulphate.2 

Procedure,  i  gram  of  the  sample,  100  c.c.  of  the  dichromate  solution 
and  10  c.c.  of  dilute  sulphuric  acid  (i  :  3)  are  shaken  for  5  minutes  in  a 


1  By  difference. 

2  For  the  titration  of  thiosulphate  solution,  see  Chrome  Steels. 


244  LEAD   AND   ITS  ALLOYS 

bottle  holding  about  200  c.c.  and  fitted  with  a  ground  stopper.  After 
addition  of  a  further  quantity  of  10  c.c.  of  dilute  sulphuric  acid,  the  shaking 
is  continued  for  10-15  minutes — until  all  the  zinc  is  dissolved.  The  bottle 
is  emptied  and  washed  into  a  half-litre  measuring  flask  and  made  up  to 
volume.  100  c.c.  of  the  solution  are  acidified  with  5  c.c.  of  hydrochloric 
acid  (D  =  i-io)  and  treated  with  10  c.c.  of  10%  potassium  iodide 
solution,  the  iodine  separated  being  titrated  with  sodium  thiosulphate  and 
starch  paste.  The  difference  in  c.c.  between  the  volumes  of  dichromate 
and  thiosulphate,  multiplied  by  0-01635,  gives  the  amount  of  zinc  in  0-2 
gram  of  the  sample. 


* 
*  * 


Commercial  zinc  dust  contains  80-90%  Zn,  9-10%  ZnO,  1-5-2%  Pb,  and 
small  quantities  of  copper,  cadmium,  arsenic,  antimony,  iron,  sulphur,  silica, 
carbon,  etc.,  and,  sometimes,  of  calcium  and  magnesium  oxides. 


LEAD    AND   ITS    ALLOYS 

Lead  is  largely  used  as  such  and  also  enters  into  the  composition  of 
numerous  alloys. 

Methods  will  be  given  here  for  the  analysis  of  commercial  lead  and  of 
hard  lead,  alloys  of  lead  with  tin  and  antimony  (solder,  white  antifriction 
metal,  white  metal  for  fittings,  etc.)  being  treated  under  tin  and  its  alloys. 

LEAD 

The  analysis  of  commercial  lead  consists  in  determining  the  impurities 
present  (silver,  copper,  bismuth,  cadmium,  arsenic,  antimony,  iron,  nickel, 
cobalt,  zinc  and  manganese).  These  impurities  are,  however,  present  in 
very  small  proportions  (refined  lead  contains,  indeed,  99*96-99-99%  Pb), 
and  it  is  therefore  necessary  to  employ  large  quantities  of  the  sample  and 
to  conduct  all  the  analytical  operations  with  the  greatest  precision. 

In  a  i -5-litre  beaker,  200  grams  of  the  metal  are  gently  heated  with  a 
mixture  of  500  c.c.  of  nitric  acid  (D  1-2)  and  500  c.c.  of  water.  After  stand- 
ing for  about  12  hours,  the  liquid  is  filtered,  the  insoluble  residue  (lead 
antimonate)  being  collected  on  a  small  filter,  washed,  placed  in  a  porcelain 
crucible  and  kept  apart  (residue  a). 

The  filtrate  is  treated  with  62-63  c.c.  of  concentrated  sulphuric  acid 
and  left  to  cool  and  settle,  the  clear  supernatant  liquid  being  siphoned 
into  a  3-litre  beaker.  The  residue  is  shaken  with  200  c.c.  of  water  acidified 
with  nitric  acid,  allowed  to  settle  and  the  supernatant  liquid  added  to  the 
first  solution  ;  to  ensure  complete  washing,  this  operation  should  be  repeated 
three  or  four  times. 

The  liquid  freed  from  lead  sulphate  is  then  rendered  alkaline  with  ammo- 
nia and  treated  with  25-50  c.c.  of  colourless  ammonium  sulphide.  Together 
with  small  quantities  of  lead  which  have  passed  into  solution,  the  copper, 
silver,  bismuth,  iron,  etc.,  are  precipitated  as  sulphides,  whilst  the  arsenic 
and  antimony  remain  in  solution  in  the  alkaline  sulphide.  After  remaining 


LEAD 


245 


for  2-3  hours  on  the  water-bath,  the  liquid  is  filtered  and  the  precipitate 
washed  with  water  containing  a  little  ammonium  sulphide  and  added  to 
the  residue  in  the  porcelain  crucible  (residue  a),  which  is  then  carefully 
ignited.  The  oxides  thus  obtained  are  fused  with  sodium  carbonate  and 
sulphur  (see  Gravimetric  Analysis  of  Ordinary  Bronzes),  the  fused  mass 
being  extracted  with  water  and  the  solution  reduced  with  sulphite  and 
filtered.  The  filtrate  is  added  to  the  alkaline  sulphide  solution  and  the 
whole  used  for  the  determination  of  the  antimony  and  arsenic  (see  3)  ;  on 
the  filter  the  other  impurities  remain  as  sulphides. 

The  precipitate  thus  obtained  is  dissolved  in  nitric  acid  (i  vol.  of  nitric 
acid,  D  =  1-2,  and  2  vols.  of  water)  and  the  liquid  evaporated  with  a  slight 
excess  of  sulphuric  acid  to  eliminate  the  smah1  quantities  of  lead  still  present 
and  to  expel  the  nitric  acid  (excess  of  sulphuric  acid  is  necessary  to  keep 
the  bismuth  in  solution)  ;  the  residue  is  taken  up  in  a  little  water,  filtered 
and  treated  with  hydrogen  sulphide.  Bismuth,  silver,  cadmium  and  copper 
sulphides  are  precipitated  (see  i),  whilst  nickel,  cobalt,  iron,  zinc  and  man- 
ganese remain  in  solution  (see  2). 

1.  Determination  of  the  Bismuth,  Silver,  Cadmium  and  Copper. 
—The  sulphides  precipitated  with  hydrogen  sulphide  are  dissolved  in  nitric 
acid  and  the  solution  evaporated  in  presence  of  sulphuric  acid. 

(a)  DETERMINATION  OF  THE  BISMUTH.    The  residue  is  dissolved  in  a 
little  water,  almost  neutralised  with  pure  sodium  hydroxide,  treated  with 
sodium  carbonate  in  slight  excess  and  with  a  little  potassium  cyanide  and 
gently  heated.     If  bismuth  is  present,  a  white  precipitate  is  obtained,  this 
being  filtered  off,  well  washed  and   dissolved  in  a  little  nitric  acid.    The 
bismuth  is  then  precipitated  with  a  slight  excess  of  ammonia,  the  precipi- 
tate being  washed  and  dissolved  in  nitric  acid  and  the  solution  evaporated 
in  a  tared  porcelain  crucible ;   the  residue  is  ignited  gently  and  weighed  : 
Bi2O3  x  0-8965  =  Bi. 

(b)  DETERMINATION^  THE  SILVER.1    The^  filtrate  from  the  treatment 
with  sodium  carbonate  and  potassium  cyanide  is  treated  with  a  little  more 
potassium  cyanide  and  a  few  drops  of  sodium  sulphide,  the  silver  and  cad- 
mium being  precipitated  as  sulphides,  while  any  copper  present  remains 
in  solution.     The  precipitate  is  collected,  washed,  dissolved  in  nitric  acid 
and  the  silver  precipitated  as  chloride  by  addition  of  a  few  drops  of  dilute 
hydrochloric  acid  :    AgCl  x  07526  =  Ag. 

(c)  DETERMINATION  OF  THE  CADMIUM.    The  filtrate  from  the  silver 
chloride  is  evaporated  almost  to  dryness  and  treated  at  the  boiling  point 
with  sodium  carbonate.    The  precipitate  formed  is  collected,  washed  with 
hot  water,  dissolved  in  a  little  nitric  acid,  evaporated  in  a  tared  porcelain 
crucible,  gently  ignited  and  weighed :    CdO  X  0-8754  =  Cd. 

(d)  DETERMINATION  OF  THE  COPPER.    The  nitrate  from  the  silver  and 
cadmium  sulphides  (see  b)  is  treated  with  a  little  sulphuric  and  nitric  acids 
and  a  few  drops  of  hydrochloric  acid  and  evaporated  to  dryness.     The 
residue  is  dissolved  in  water  and  the  copper  determined  electrolytically  or 
gravimetrically. 

1  The  silver  is  more  exactly  determined  directly  by  cupellation  (see  Silver  and  its 
Alloys). 


246  LEAD 

2.  Determination  of  the  Nickel,  Cobalt,  Iron,  Zinc  and  Man- 
ganese.— The  filtrate  from  the  bismuth,  silver,  cadmium  and  copper  sul- 
phides is  collected  in  a  flask,  rendered  slightly  ammoniacal  and  treated  with 
3  c.c.  of  ammonium  sulphide.  The  flask  is  filled  with  water  and  left  closed 
for  24  hours,  after  which  the  precipitate  is  collected,  washed  with  hot  water 
containing  a  few  drops  of  ammonium  sulphide  and  treated  on  the  filter 
with  a  mixture  of  5  parts  of  saturated  hydrogen  sulphide  solution  and  I 
part  of  hydrochloric  acid  (D  1-2).  The  iron,  zinc  and  manganese  sulphides 
are  dissolved  and  these  metals  are  determined  as  in  (b)  and  (c)  ;  nickel 
and  cobalt  sulphides  remain  on  the  filter  and  are  determined  as  in  (a). 

(a)  DETERMINATION  OF  THE   NICKEL  AND   COBALT.    The  nickel  and 
cobalt  sulphides,  which  have  remained  undissolved,  are  ignited  and  weighed 
as  oxides,  which  are  then  dissolved  in  aqua  regia,  the  solution  rendered 
alkaline  with  ammonia,  and  the  nickel  precipitated  with  dimethylglyoxime 
(see  Argentan). 

(b)  DETERMINATION  OF  THE  IRON.     The  hydrogen  sulphide  is  expelled 
by  boiling  from  the  hydrochloric  acid  solution  containing  the  iron,  zinc 
and  manganese,  oxidation  being  effected  by  a  few  drops  of  nitric  acid  and 
the  liquid  made  alkaline  with  ammonia.     The  precipitated  ferric  hydroxide 
is  collected,  washed  and  dissolved  in  hydrochloric  acid,  the  iron  being  then 
reprecipitated  with  ammonia  and  weighed  as  ferric  oxide  :   Fe203  X  0-6994 
=  Fe. 

(c)  DETERMINATION  OF  THE  ZINC.     The  filtrates  from  the  iron  precipi- 
tate are  together  rendered  alkaline  with  ammonia  and  treated  in  a  flask 
with  2-3  c.c.  of  ammonium  sulphide,  the  flask  being  then  filled  with  water, 
stoppered  and  left  for  24  hours.     The  zinc  and  manganese  sulphides  are 
then  collected,  washed  and  treated  on  the  filter  with  dilute  acetic  acid, 
which  dissolves  only  the  manganese  sulphide.     The  residue,  consisting  of 
zinc  sulphide,  is  dissolved  on  the  filter  by  dilute  hydrochloric  acid  and  the 
solution  evaporated  to  dryness  in  a  tared  crucible.     The  residue  is  mixed 
with  an  aqueous  suspension  of  a  little  pure  mercuric  oxide  free  from  alkali, 
evaporated  to  dryness,  heated  gently  over  a  naked  flame  to  eliminate  the 
mercury,  ignited  over  a  blowpipe  flame  and  weighed  :  ZnO  X  0-8034  =  Zn. 

(d)  DETERMINATION  OF  THE  MANGANESE.    The  acetic  acid  solution  of 
the  manganese  is  concentrated  and  treated  with  ammonia  and  hydrogen 
peroxide  to  precipitate  the  manganese,  the  precipitate  being  collected, 
washed,  dried,  ignited  and  weighed  :    Mn3O4  X  0-7203  =  Mn. 

3.  Determination  of  the  Arsenic  and  Antimony. — (a)  DETERMI- 
NATION OF  THE  ARSENIC.  The  alkaline  sulphide  solution  obtained  as 
described  on  p.  245  is  acidified  with  acetic  acid  and  heated  for  3-4  hours 
on  the  water-bath,  the  arsenic  and  antimony  sulphides  and  sulphur  which 
separate  being  filtered  off.  The  precipitate  is  washed  with  saturated 
hydrogen  sulphide  solution  slightly  acidified  with  acetic  acid,  dried,  freed 
from  sulphur  by  means  of  carbon  disulphide,  filtered,  and  the  arsenic  and 
antimony  sulphides  dissolved  in  hydrochloric  acid  and  potassium  chlorate. 
The  liquid  is  filtered  through  a  small  filter,  and  the  filtrate  treated  with 
0-5  gram  of  tartaric  acid  and  neutralised  with  ammonia  ;  the  solution, 
which  should  occupy  about  20  c.c.,  is  then  treated  with  10  c.c.  of  concen- 


HARD   LEAD 


247 


trated  ammonia  and  1-2  c.c.  of  magnesia  mixture.  After  about  24  hours, 
the  magnesium  ammonium  arsenate  is  collected  on  a  filter,  transformed 
by  ignition  into  pyroarsenate  and  weighed  :  Mg2As2O7  x  0-4827  =  As. 

(b)  DETERMINATION  OF  THE  ANTIMONY.  The  nitrate  from  the  mag- 
nesium ammonium  arsenate  is  treated  with  ammonium  sulphide  and  acidified 
slightly  with  sulphuric  acid.  The  antimony  is  thus  precipitated  as  sulphide, 
which  is  dissolved  in  ammonium  sulphide,  the  solution  being  evaporated 
in  a  tared  porcelain  crucible,  oxidised  with  nitric  acid,  calcined  gently  and 
weighed  :  Sb2O4  x  0-7898  =  Sb. 


The  refined  lead  of  commerce,  especially  that  destined  for  making  electrical 
accumulator  plates,  is  a  very  pure  metal,  containing  99-96-99-99%  Pb. 

The  compositions  of  samples  of  lead  of  different  origins  are  as  follows 
(Schnabel,  Hollard,  Hampe)  : 

TABLE   XXIX 
Composition  of  Samples  of  Lead 


Origin. 

Pb 

Sb 

Ag 

Cu           Zn 

Fe 

Bi 

As 

Cd 

Ni 

Mn 

Pertusola  j  *  ' 

99-99I5 

0-0050 

o-ooi 

0-0003 

0-0006 

0-0016 











99-9937 

0-0013 

0-0006 

— 

0-00085 

0-0014 

O-OO2I 

— 

— 

— 

— 

Monteponi  (Sardinia) 

99-99 

0-0030 

o-ooio 

0-0005 

O-OO2I 

0-0047 

O-OOO7 

— 

—    . 

— 

Pennsylvania   (Lead 

Co.)       .... 

99-9924 

O-OOI2 

O-OOO2 

0-O002 

0-0007 

0-0017 

O-OO3O 

— 

— 

0-0002 

Germany. 

99-9852 

0-0044 

0-0006 

O-OOO7     O-OOO5 

O-OOII 

0-0073 

trace 

trace 



Zn,Ni,Co 

Spain  (Penarroya)    . 

99-989 

0-003  !   — 

trace 

^—  •—**—  -v 
0-005 

0-012 

O-Ogi 







* 
i 

Sweden    .... 

99-9575 

0-0040 

trace 

0-0018 

O-O002 

0-OOI5 

0-0350 

trace 

trace 

— 

i 

HARD    LEAD 

Hard  lead  or  antimonial  lead  is  an  alloy  of  lead  and  antimony  con- 
taining small  quantities  of  copper  and  tin  and  sometimes  also  iron,  nickel, 
cadmium,  arsenic,  etc.,  and  serves  for  making  type,  the  plates  of  certain 
forms  of  electric  accumulators  and  cast  ornamental  articles,  and  as  anti- 
friction metal,  etc. 

The  essential  determinations  to  be  made  on  these  alloys  for  a  complete 
analysis  (see  B)  are  those  of  the  lead,  antimony,  copper  and  tin,  determina- 
tions of  iron,  nickel,  arsenic,  etc.,  not  being  always  necessary.  Often, 
however,  determinations  of  certain  elements  only  are  required  (see  Partial 
Analysis). 

A.    Partial  Analysis 

For  special  purposes,  determinations  of  the  copper  and  tin  alone  are 
required. 

1.  Direct  Determination  of  the  Copper. — See  Direct  Determination 
of  Copper  in  White  Metal. 


248  HARD   LEAD 

2.  Direct  Determination  of  the  Tin. — From  2  to  4  grams  of  the 
sample  in  fine  filings  are  heated  to  boiling,  in  an  inclined  long-necked  flask 
covered  with  a  funnel,  with  20  c.c.  of  cone,  sulphuric  acid  until  the  lead 
sulphate  separating  appears  perfectly  white.  The  cold  mass  is  treated 
with  2-3  grams  of  tartaric  acid  dissolved  in  a  little  water  and  the  whole 
introduced  quantitatively  into  a  100  c.c.  measuring  flask,  made  up  to  volume, 
mixed  and  filtered  through  a  dry,  pleated  filter.  50  c.c.  of  the  filtrate 
are  rendered  alkaline  with  ammonia,  heated  gently  with  5  grams  of  oxalic 
acid  and  the  clear  solution  treated  with  5  grams  of  ammonium  oxalate, 
diluted  to  about  150  c.c.  and  kept  gently  boiling  during  the  passage  of 
hydrogen  sulphide  to  precipitate  the  antimony  and  copper.  After  about 
an  hour,  the  liquid  is  allowed  to  cool  a  little  and  filtered,  i%  oxalic  acid 
solution  saturated  with  hydrogen  sulphide  being  used  for  washing. 

The  filtrate  is  boiled  for  a  short  time  with  30  c.c.  of  hydrochloric  acid 
and  20  grams  of  ammonium  oxalate  to  expel  the  hydrogen  sulphide.  After 
being  allowed  to  cool  somewhat,  the  liquid  is  treated  with  a  few  drops  of 
hydrogen  peroxide,  heated  a  short  time,  made  up  to  about  300  c.c.,  cooled 
to  50-60°  and  electrolysed — turbid  with  sulphur  as  it  often  is — to  deter- 
mine the  tin  :  coppered  Winkler  cathode,  spiral  Winkler  anode,  ND100 
=  i  amp.,  temperature  about  50°,  duration  (0-1-0-3  gram  Sn)  4-5  hours. 

Since  the  antimony  and  copper  sulphides  precipitated  may  retain  small 
amounts  of  tin,  for  an  exact  analysis  the  precipitation  should  be  carried 
out  twice.  These  sulphides  are,  therefore,  dissolved  in  the  hot  in  a  mixture 
of  10-15  c.c.  of  cone,  hydrochloric  acid,  10-15  c.c.  of  10%  ammonium 
chloride  solution  and  a  few  crystals  of  potassium  chlorate,  the  solution 
being  diluted  with  a  little  water,  filtered,  rendered  alkaline  with  ammonia, 
treated  with  5  grams  of  oxalic  add  and  5  grams  of  ammonium  oxalate, 
diluted  to  100  c.c.  and  subjected  at  the  boiling  point  to  a  current  of  hydrogen 
sulphide.  After  about  an  hour,  the  liquid  is  filtered  and  the  precipitate 
washed  with  the  oxalic  solution  saturated  with  hydrogen  sulphide.  The 
two  filtrates  are  united  and  the  solution — concentrated  if  necessary — or 
an  aliquot  part  of  it  used  for  the  electrolytic  determination  of  the  tin. 

B.    Complete    Analysis 

In  a  250  c.c.  measuring  flask,  2-5  grams  of  the  sample  in  fine  filings 
are  gently  heated  with  15  c.c.  of  water  and  10  grams  of  powdered  tartaric 
acid  until  the  latter  dissolves,  4-5  c.c.  of  nitric  acid  being  added  gradually 
and  with  shaking,  and  the  liquid  left  until  the  metal  is  completely  dissolved. 
4  c.c.  of  cone,  sulphuric  acid  are  then  added  and  the  cooled  liquid  made 
up  to  volume  and  mixed,  and,  after  a  brief  stand,  filtered  through  a  tared 
Gooch  crucible  into  a  dry  vessel.  Of  the  filtrate  50  c.c.  ( =  0-5  gram  of 
alloy)  are  used  for  the  determination  of  the  antimony  (see  2)  and  100  c.c. 
(=  i-o  gram  of  alloy)  for  that  of  the  tin  and  copper  (see  3). 

1.  Determination  of  the  Lead. — When  these  two  portions  of  the  ni- 
trate are  removed,  the  whole  of  the  lead  sulphate  in  the  250  c.c.  flask  is  trans- 
ferred to  the  Gooch  crucible  and  is  washed,  first  with  a  mixture  of  250  c.c. 
of  water,  10  grams  ot  tartaric  acid  and  4  c.c.  of  sulphuric  acid  and  then  with 


HARD   LEAD  249 

95%  alcohol  until  the  reaction  is  neutral,  and  subsequently  dried,  heated  in 
an  air-bath,  cooled  in  a  desiccator  and  weighed  :  PbSO4  X  0-6831  =  Pb. 

2.  Determination  of  the  Antimony. — The  50  c.c.  of  solution  taken 
is  concentrated  to  20-30  c.c.,  neutralised  with  50%  sodium  hydroxide 
solution,  an  excess  of  3-4  c.c.  of  the  latter  and  30  c.c.  of  sodium  sulphide 
solution  (D  1-225)  added  and  the  liquid  heated  and,  after  some  time,  filtered 
to  remove  the  copper  sulphide,  etc.,  directly  into  a  tared  Classen  capsule  ; 
the  precipitate  is  washed  with  hot  water  in  which  a  little  sodium  sulphide 
is  dissolved.     The  nitrate  is  treated  with  50  c.c.  of  sodium  sulphide  and 
5-6  grams  of  pure  potassium  cyanide,  mixed  and  electrolysed  to  determine 
the  antimony,    ND100  =  o-i5-o-i8    amp.,  voltage  =  1-1-2,    duration  (o'l- 
0-15  gram  Sb)  15-18  hours.     When  the  deposition  is  complete,  the  capsule 
is  emptied,  thoroughly  washed  with  water,  alcohol  and  ether,  dried  at  70° 
and  weighed. 

3.  Determination  of  the  Tin  and  Copper. — The  100  c.c.  of  solution 
taken  is  rendered  slightly  alkaline  with  ammonia,  treated  with  5  grams 
of  oxalic  acid,  heated  to  obtain  a  clear  solution,  treated  with  7  grams  of 
ammonium  oxalate,  and  kept  boiling  for  about  an  hour  while  a  stream  of 
hydrogen  sulphide  is  passed  to  precipitate  the  antimony  and  copper.     When 
the  liquid  has  cooled  somewhat  in  the  current  of  hydrogen  sulphide,  it  is 
filtered  into  a  half-litre  beaker,  the  filter  being  washed  with  a  hot  i%  oxalic 
acid  solution  saturated  with  hydrogen  sulphide. 

(a)  DETERMINATION  OF  THE  TIN.    The  nitrate  is  treated  with  30  c.c. 
of  cone,  hydrochloric  acid  and  20  grams  of  ammonium  oxalate  and  boiled 
for  a  short  time  to  expel  hydrogen  sulphide.     After  the  liquid  has  cooled 
somewhat,  a  few  drops  of  30%  hydrogen  peroxide  are  added  and  the  solu- 
tion heated  for  a  little  while,  made  up  to  300  c.c.,  cooled  to  40-45°  and — 
often  turbid  with  sulphur — electrolysed  to  determine  the  tin  :    coppered 
Winkler  cathode,  spiral  anode,  ND100  —  i  amp.,  voltage  =  3-4,    tempera- 
ture =  40-50°,   duration   (o-i-o-3  gram  Sn)  =  4-5  hours   (see  also  Elec- 
trolytic Determination  of  Tin  in  Ordinary  Bronzes). 

(b)  DETERMINATION   OF  THE   COPPER.    The   precipitated   copper   and 
antimony  sulphides,  which  have  been  filtered  off,  are  heated  gently  with 
i%  sodium  hydroxide  solution  and  filtered,  the  filter  being  thoroughly 
washed  with  water  faintly  alkaline  with  sodium  hydroxide  ;    the  copper 
sulphide  remains  undissolved.     The  filter-paper  and  precipitate  are  dried 
in  a  small  dish,  the  filter  incinerated,  the  residue  dissolved  in  nitric  acid, 
and  the  copper  determined  in  this  solution  by  the  usual  method  (see  Deter- 
mination of  Copper  in  Ordinary  Brass).1 

4.  Determination    of   the  Iron,  Nickel    and    Zinc. — 5  grams    of 
the  sample  are  treated  with  nitric  acid  (D  =1*2),  the  solution  being  left 
on  the  water-bath  for  a  short  time  and  then  filtered  ;  the  filtrate  is  treated 
with  excess  of  sulphuric  acid  and  evaporated  to  complete  elimination  of 
the  nitric  acid.     The  residue  is  taken  up  in  water,  filtered,  treated  with 
hydrogen  sulphide  and  filtered  again,  the  filtrate  being  used  for  the  deter- 
mination of  the  iron,  zinc  and  nickel  as  in  argentan. 

1  It  should  be  borne  in  mind  that  cadmium  may  sometimes  be  present  as  well  as 
copper. 


250  ANTIMONY   AND   ITS   ALLOYS 

5.  Determination  of  the  Arsenic. — See  Copper. 

*** 

Hard  lead  contains  variable  quantities  of  antimony  (usually  10-25%) 
and  may  contain  small  amounts  of  copper,  tin,  iron,  nickel,  arsenic,  etc. 

The  following  table  contains  the  results  of  analysis  of  samples  of  hard  lead, 
obtained  directly,  from  o  res  of  lead  and  antimony  (Schnabel)  : 

TABLE   XXX 
Composition  of  Hard  Leads 


Source. 

Pb 

Sb 

Cu 

As 

Sn 

(I      .       .       .       . 

81-71 

17-69 

0-62 



_ 

Oberharz^II    .... 

82-44 

16-90 

0-68 

— 

—  . 

\III.      .      .      . 

82-08 

17-34 

•   0-62 

— 

— 

Freiberg     

15 

" 

2-5 

°'3 

ANTIMONY    AND    ITS    ALLOYS 

Owing  to  its  brittleness,  antimony  is  rarely  used  as  such,  but  it  forms 
part  of  many  industrial  alloys,  such  as  white  bearing  metals,  type  metal,  etc. 

Methods  for  determining  the  impurities  commonly  accompanying  com- 
mercial antimony  are  therefore  described,  since  the  value  depends  on  the 
purity. 

Lead-antimony  alloys  are  treated  under  lead,  while  alloys  of  antimony 
with  tin  alone  or  with  tin  and  lead  together  (white  metals)  are  dealt  with 
along  with  tin. 


ANTIMONY 

Analysis  of  commercial  antimony  is  generally  limited  to  the  determina- 
tion of  its  commoner  impurities  :  lead,  bismuth,  copper,  iron,  arsenic  and 
sulphur. 

10  grams  of  the  finely  powdered  sample  are  treated  with  aqua  regia 
(140  c.c.  HC1,  20  c.c.  HN03)  diluted  with  an  equal  volume  of  water,  the 
solution  thus  obtained  being  treated  with  60-70  c.c.  of  50%  tartaric  acid 
solution,  then  made  alkaline  with  concentrated  sodium  hydroxide  solution 
and  subjected  to  a  current  of  hydrogen  sulphide.  The  separation  of  the 
sulphides  is  facilitated  by  heating  on  a  water-bath,  the  precipitate  being 
filtered  off  and  washed  once  or  twice  with  hot  water  containing  a  few  drops 
of  sodium  sulphide.  The  precipitate  is  then  dissolved  in  a  little  hydro- 
chloric acid  containing  bromine  and  1-2  drops  of  tartaric  acid  added  to 
the  solution,  which  is  rendered  alkaline  with  sodium  hydroxide  and  again 
precipitated  with  hydrogen  sulphide  to  ensure  the  complete  elimination 
of  the  antimony.  After  a  short  rest  on  the  water-bath,  the  liquid  is  filtered 


ANTIMONY  251 

and  the  sulphides  washed  thoroughly  with  hot  water  containing  a  little 
sodium  sulphide  and  dissolved  in  nitric  acid  (D  1-2). 

1 .  Determination  of  the  Lead . — The  nitric  acid  solution  is  evaporated 
in  presence  of  excess  of  sulphuric  acid  until  white  fumes  appear,  taken  up 
in  a  little  water  and  mixed  with  a  few  c.c.  of  95%  alcohol  ;    after  some 
time,  the  lead  sulphate  separated  is  collected  in  a  Gooch  crucible  as  indi- 
cated for  the  determination  of  lead  in  ordinary  brasses  (see  p.  226). 

2.  Determination    of   the    Bismuth. — The   liquid   freed   from   lead 
sulphate  is  heated  to  expel  the  alcohol  and  treated  with  hydrogen  sulphide 
to  precipitate  the  bismuth  and  the  copper.     The  precipitate  is  filtered  off, 
washed  with  hydrogen  sulphide  solution  acidified  with  a  few  drops  of  sul- 
phuric acid,  and  dissolved  in  a  little  nitric  acid  (D  1-2).     The  solution  is 
evaporated  in  presence  of  sulphuric  acid,  taken  up  in  a  little  water,  neu- 
tralised  almost   completely   with   sodium   hydroxide,    and   heated   gently 
with  a  slight  excess  of  sodium  carbonate  and  a  little  potassium  cyanide. 
The  bismuth  precipitate  thus  obtained  is  collected  on  a  filter,  washed, 
dissolved  in  nitric  acid  and  again  precipitated  with  ammonia  under  the 
conditions  indicated  for  the  determination  of  bismuth  in  lead. 

3.  Determination  of  the  Copper.— The  filtrate  from  the  bismuth — 
after  treatment  with  sodium  carbonate  and  potassium  cyanide  (see  2) — 
is  acidified  with  nitric  acid  and  a  few  drops  of  sulphuric  acid,  evaporated 
to  dryness,  taken  up  in  hot  water  and  the  copper  in  the  solution  determined 
by  the  usual  methods. 

4.  Determination  of  the  Iron. — The  filtrate  obtained  after  removal 
of  the  bismuth  and  copper  as  sulphides  (see  2)  contains  all  the  iron,  which 
is  determined  by  expelling  the  excess  of  hydrogen  sulphide,  oxidising  with 
nitric  acid  and  precipitating  with  ammonium  chloride  and  ammonia. 

5.  Determination  of  the  Arsenic. — See  Determination  of  Arsenic  in 
Copper. 

6.  Determination    of    the    Sulphur     (Hollard    and    Bertiaux). — 5 
grams  of  the  sample  are  treated  with  nitric  acid  to  which  sufficient  hydro- 
chloric acid  is  added  to  give  a  clear  solution.     The  liquid  is  evaporated  to 
dryness,  taken  up  again  in  nitric  acid  and  evaporated  several  times  with 
nitric  acid  to  expel  the  hydrochloric  acid  completely.     The  residue  is  finally 
treated  with  water  faintly  acidified  with  nitric  acid  and  the  solution  filtered 
and  the  residue  washed  with  water.     To  the  filtrate  sufficient  ammonia 
is  added  to  redissolve  the  antimony  oxide  at  first  separating,  excess  of 
nitric  acid  being  then  added  and  the  liquid  filtered.     In  the  clear  solution 
the  sulphuric  acid,  formed  by  oxidation  of  the  sulphur  in  the  sample,  is 
precipitated  by  means  of  barium  nitrate. 


*** 


Commercial  antimony  generally  contains  small  quantities  of  lead,  copper, 
iron,  sulphur  and,  sometimes,  bismuth,  nickel  and  cobalt.  Pure  antimony 
is  silvery  white,  but  the  commercial  metal  has  a  slightly  bluish  tint  owing  to 
the  impurities  present.  It  exhibits  a  marked  tendency  to  crystallise  and,  indeed, 
usually  has  a  crystalline  structure,  which  is  manifested  even  on  the  outside  by 
large  crystals  resembling  fern  leaves,  these  being  regarded — not  always  witli 
reason — as  a  sign  of  the  purity  of  the  metal. 


252 


TIN  AND   ITS  ALLOYS 


The  compositions  of  various  samples  of  antimony  of  different  origin  are  as 
follows  (Schnabel)  : 

TABLE   XXXI 
Results  of  Analyses  of  Antimony 


Origin.                             Sb 

Cu 

Fe 

Pb 

As 

Bi 

S 

Ni  +  Co 

Hungary  (Liptau)  .      .     98-27 

o-54 

0-63 

_ 

_ 

0-36 

_ 

,  . 

^  ,.,       .    f  I       .      .      .     98-34 
California  4  TT 
(II     .      .      .     99-081 

O-O2I 
0-052 

0-144 
0-039 

0-410 
0-538 

i  -oo  8 
0-036 

i 

0-064 
0-254 

0-013 
trace 

Of  various  origins    )I      98-98 

O-OI 

o-35 

o-34 

0-09 

— 

0-23 

— 

(analysis  by  Hilmy)  [II    98-87 

O-O2 

0-16 

°73 

0-09 



O-II 

" 

TIN   AND   ITS   ALLOYS 

Tin  is  one  of  the  most  important  metals,  being  largely  used  as  such  and 
also  as  a  constituent  of  numerous  industrial  alloys. 

Methods  will  be  given  here  for  the  determination  of  elements  occurring 
in  commercial  tin  as  impurities,  for  the  analysis  of  tin-plate  and  the  more 
important  tin  alloys  (phosphor-tin,  solder,  white  antifriction  metals,  type 
metal  and  metal  for  fittings). 

Alloys  of  tin  with  copper  (bronzes)  are  considered  along  with  copper. 

TIN 

Commercial  tin  is  usually  contaminated  by  small  quantities  of  lead, 
copper,  iron,  bismuth,  antimony,  sulphur,  and  arsenic  and  sometimes  traces 
of  molybdenum,  tungsten,  zinc,  manganese,  nickel,  chromium,  etc.  The 
more  important  determinations  are  those  of  lead,  bismuth,  copper,  iron, 
antimony,  arsenic  and  sulphur,  qualitative  tests  for  the  other  elements 
being  sufficient. 

1.  Determination  of  the  Lead,  Bismuth,  Copper  and  Iron.— 
According  to  the  greater  or  less  degree  of  impurity,  from  10  to  20  grams 
of  the  sample,  flattened  on  an  anvil  or  in  a  small  rolling  mill  and  cut  up 
fine,  are  heated  gently  on  a  water-bath  with  aqua  regia  (i  vol.  of  nitric 
acid  with  5  vols.  of  hydrochloric  acid  ;  10  grams  of  the  sample  require  140 
c.c.,  and  20  grams,  180  c.c.).  When  the  metal  is  completely  attacked,  the 
liquid  is  allowed  to  cool  and  treated,  according  to  the  weight  of  sample 
taken,  with  25-35  grams  of  tartaric  acid  ;  the  latter  is  dissolved  by  gentle 
heating,  the  liquid  then  rendered  alkaline  with  20%  sodium  hydroxide 
solution,  and  25  c.c.  of  2%  sodium  sulphide  solution  added  with  continual 
shaking.  Separation  of  the  lead,  bismuth,  copper  and  ferric  sulphides  is 
facilitated  by  heating  for  some  time  on  the  water-bath,  the  precipitate  being 
ultimately  filtered  off  and  washed  with  dilute  sodium  sulphide  solution. 

(a)  DETERMINATION    OF   THE   LEAD.    The   precipitate   obtained   with 


TIN  253 

sodium  sulphide  is  dissolved  in  a  little  nitric  acid  (D  1-2)  and  the  solution 
evaporated  in  presence  of  sulphuric  acid  until  white  fumes  appear  ;  the 
residue  is  treated  with  water,  alcohol  added  and  the  lead  sulphate  collected 
on  a  closely-woven  filter  paper.  As  it  may  contain  small  quantities  of 
tin,  the  precipitate  is  redissolved  in  ammonium  acetate  solution  and  the 
lead  reprecipitated  with  hydrogen  sulphide  and  converted  into  sulphate, 
which  is  collected  on  a  Gooch  crucible  as  usual  (see  Gravimetric  Determina- 
tion of  Lead  in  Ordinary  Brass). 

(b)  DETERMINATION   OF  THE  BISMUTH  AND  COPPER.    The    alcohol  is 
expelled  from  the  liquid  separated  from  the  first  lead  sulphate  precipitate 
and  the  bismuth  and  copper  precipitated  with  hydrogen  sulphide  and 
determined  as  in  the  analysis  of  antimony. 

(c)  DETERMINATION  OF  THE  IRON.    The  iron  is  determined  as    oxide 
in  the  filtrate  from  the  bismuth  and  copper  sulphides  (see  Determination 
of  Iron  in  Antimony). 

2.  Determination  of  the  Antimony. — 10  grams   of   the   sample  are 
treated  with  100  c.c.  of  hydrochloric  acid  (D  1-124)  and  potassium  chlorate, 
the  chlorine  eliminated  by  boiling,  the  volume  made  up  to  about  250  c.c., 
and,  while  the  liquid  is  heated  on  the  water-bath,  6  grams  of  pure  reduced 
iron  added  in  small  quantities  to  displace  the  copper  and  antimony.     The 
separated  metals,  together  with  the  small  amount  of  undissolved  iron, 
are  filtered  off  and  washed  on  the  filter  with  dilute  hydrochloric  acid  until 
the  filtrate  no  longer  gives  the  reaction  for  tin  with  mercuric  chloride.     The 
separated  metals  are  then  dissolved  in  hydrochloric  acid  and  potassium 
chlorate,  the  excess  of  chlorine  expelled  by  boiling,  the  copper  and  antimony 
precipitated  with  hydrogen  sulphide  and  the  precipitate  well  washed  and 
treated  with  30  c.c.  of  sodium  sulphide  solution  (D  1-225)  to  dissolve  the 
antimony  sulphide.     The  liquid  is  filtered  directly  into  the  Classen  dish, 
the  filter  washed  with  50  c.c.  of  the  sodium  sulphide  solution,  and  the  filtrate, 
with  the  addition  of  5  -6  grams  of  potassium  cyanide,  electrolysed  to  deter- 
mine the  antimony  (see  Determination  of  Antimony  in  Hard  Lead). 

3.  Determination   of  the   Arsenic. — (a)  10  grams    of    the    sample 
are  dissolved  in  a  solution  of  100  grams  of  ferric  chloride  in  100  c.c.  of  water, 
excess  of  cone,  hydrochloric  acid  being  added  and  the  arsenic  distilled  in 
the  ordinary  way  (see  Determination  of  Arsenic  in  Iron). 

(b)  ic  grams  of  the  sample  are  dissolved  in  hydrochloric  acid  contain- 
ing potassium  chlorate,  the  chlorine  being  expelled  by  boiling,  and  the 
cold  liquid  mixed  with  one-third  of  its  volume  of  cone,  hydrochloric  acid 
and  hydrogen  sulphide  passed  through  it  for  some  hours.  The  arsenic 
sulphide  thus  precipitated  is  filtered  off  on  an  asbestos  filter  (Gooch  crucible), 
washed  with  cone,  hydrochloric  acid  and  then  with  boiled  water  and  dis- 
solved in  ammonia  ;  the  solution  is  evaporated  in  a  dish  and  the  residue 
dissolved  in  cone,  nitric  acid,  made  strongly  alkaline  with  ammonia  and 
the  arsenic  precipitated  with  magnesia  mixture  and  alcohol.  The  precipi- 
tate is  collected,  washed,  transformed  into  pyroarsenate  and  weighed. 

4.  Determination  of  the  Sulphur. — See  Determination  of  Sulphur  in 
Iron. 


254 


TIN-PLATE 


Tin  of  good  quality  should  be  white  and  lustrous  and  of  crystalline  structure 
and,  if  in  rods,  it  should  give  the  characteristic  crackling  when  bent  in  different 
directions.  It  should  not  contain  more  than  0-1%  of  sulphur  and  arsenic 
together,  or  more  than  0-01%  of  bismuth,  or  more  than  i%  of  total  impurities. 

The  compositions  of  tins  of  different  origin  are  as  follows  (Hollard,  Schnabel) : 

TABLE    XXXII 
Composition  of  Samples  of  Tin 


Source. 

Sn 

Pb 

Fe 

Cu           Bi 

Sb 

A. 

Straits           j'Banka 

99-961 

0-014     0-019 

0-006 

Settlements  <  Malacca    . 

99-805 

O-O2O 

0-072        — 

0-060 

0-043 

i^Pulo  Brani 

99-76 

O-O2         0-14 

0-07 

— 

China  (Hong-  Kong) 

98-928 

0-833      0-037 

0-040                  0-044 

0-118 

England        

99-76 

— 

trace 

0-24 

— 

(I  

Germany  j    ., 

99-336 
99-594 

— 

trace 

0-480    0-060     0-545 
0-406       — 

0-079 
trace 

TIN-PLATE 

With  commercial  tin-plate  the  most  important  determination  to  be 
made  is  that  of  the  tin,  the  thickness  of  the  layer  of  this  metal  determining 
the  value  ;  next  comes  the  determination  of  the  lead,  which  gives  an  indi- 
cation of  the  quality  of  the  tin  used.  For  these  two  determinations  see  i. 

Sometimes,  however,  for  certain  purposes  (hygienic,  for  instance)  deter- 
mination of  the  lead  alone  is  of  interest,  it  being  desired  to  ascertain  if  the 
tinning  has  been  done  with  commercial  tin  or  with  an  alloy  of  lead  and  tin. 
The  determination  of  the  lead  alone  is  described  in  2. 

1.  Determination  of  the  Tin  and  Lead. — From  i  to  2  sq.  dms.  of 
the  tin-plate  x — taken  from  the  middle  of  the  plate,  since  the  tinning  is 
often  irregular  at  the  edges — is  measured  exactly,  de-fatted  with  ether  or 
benzene  and  weighed,  so  that  the  results  may  be  referred  to  the  weight  as 
well  as  the  surface  of  the  sample.  The  measured  portion  is  cut  into  small 
squares  of  1-2  cm.  side,  these  being  heated  to  boiling  for  5  minutes  in  a 
covered  beaker  with  50  c.c.  of  10%  hydrochloric  acid  (25-30  c.c.  cone, 
hydrochloric  acid  diluted  to  100  c.c.  with  water).  The  hydrochloric  acid 
solution  is  decanted  into  a  300  c.c.  measuring  flask  and  the  metal  boiled 
for  5  minutes  with  another  50  c.c.  of  the  acid,  this  being  decanted  off  and, 
if  necessary,  the  residue  treated  a  third  time  *  the  colour  of  the  metal  should 
be  a  uniform  iron-grey  when  all  the  tin  is  dissolved.  Tin  and  lead  are 
easily  dissolved  in  the  hot  by  hydrochloric  acid  of  this  concentration,  while 
the  iron  is  attacked  but  little.2  The  residue  is  washed  with  a  little  water 
and  this  decanted  into  the  300  c.c.  flask,  the  contents  of  which  are  rendered 

1  With  a  very  irregular  sample  a  larger  quantity  is  taken. 

2  If  the  tin-plate  is  very  rich  in  lead,  a  few  drops  of  nitric  acid  are  added  to  the 
hydrochloric  acid. 


TIN-PLATE  255 

slightly  alkaline  with  ammonia,  treated  with  45-50  c.c.  of  ammonium 
sulphide  l  prepared  from  ammonia  of  D  =  0-910,  cooled,  made  up  to  volume 
and  filtered  through  a  dry  filter.  The  alkaline  sulphide  solution  serves 
for  the  determination  of  the  tin  and  the  precipitate,  consisting  of  lead  and 
iron  sulphides,  for  determining  the  lead. 

A.  DETERMINATION  OF  THE  TIN.  i.  Electrolytically.  Either  stationary 
or  rotating  electrodes  may  be  used. 

(a)  Rotating    electrodes.     100    c.c.  of   the  filtrate    are   treated   in    a 
300  c.c.    beaker   with   20-30    c.c.    of   40%    sodium   sulphite    solution  to 
reduce  the  polysulphides,  made  up  to  about  200  c.c.  and  electrolysed  at 
60°.      Coppered  and  then  tinned  Winkler  cathode  z  ",    spiral  anode,  1000 
revs,  per  minute)    temperature,  60°;    ND100,  3-3-5  amp.)    voltage,    5-6  ; 
duration,  15-20  minutes. 

When  the  electrolysis  is  complete,  the  rotation  of  the  anode  is  sus- 
pended and,  without  interrupting  the  current,  the  electrolytic  beaker  replaced 
by  one  filled  with  water  ;  after  some  time,  the  cathode  is  detached,  washed 
successively  with  water,  alcohol  and  ether,  dried  at  70°  and  weighed.  The 
weight  found,  multiplied  by  3,  gives  the  tin  contained  in  the  sample  taken. 

When  rotating  electrodes  are  used,  the  determination  of  tin  in  tin-plate 
occupies  not  longer  than  an  hour. 

(b)  Stationary  electrodes.     In  a  J-litre  conical  flask,  100  c.c.  of  the 
alkaline  sulphide  filtrate  are  treated,  under  a  draught  hood,  with  a  little 
potassium   cyanide   to   reduce   the   polysulphides,    and   hydrochloric   acid 
diluted  with  an  equal  volume  of  water  added  until  the  reaction  is  acid,  the 
flask  being  kept  covered  with  a  funnel  and  shaken  meanwhile.     When 
evolution  of  gas  ceases,  the  liquid  is  boiled  for  some  time  with  25  c.c.  of 
cone,  hydrochloric  acid  to  dissolve  the  tin  sulphide  which  separates  and 
to  coagulate  the  sulphur.     After  addition  of  25  grams  of  ammonium  oxalate 
and  dilution  to  250  c.c.,  the  liquid  is  electrolysed :  coppered  Winkler  cathode  ] 
Winkler  spiral    anode  ;    ND100  =  i  amp.  ;    voltage  =  3-4  ;    temperature, 
60°  )   duration  (for  0-1-0-5  gram  Sn),  4-5  hours  (see  also  Electrolytic  Deter- 
mination of  Tin  in  Ordinary  Bronzes).     Multiplication  by  three  of  the  tin 
found  gives  the  amount  in  the  sample  taken. 

2.  Gravimetrically .  In  a  |-litre  conical  flask,  50  or  100  c  c.  of  the  alkaline 
sulphide  filtrate  (see  i,  p.  254)  are  diluted  with  water  and  acetic  acid  added 
until  the  reaction  is  faintly  acid,  the  tin  being  thus  precipitated  as  sulphide. 
After  standing  overnight,  the  precipitate  is  filtered  off,  washed  with  10% 
ammonium  acetate  solution  and  dried  at  100-120°.  The  filter  and  precipitate 
are  introduced  into  a  tared  porcelain  crucible,  the  filter-paper  incinerated 
with  addition  of  a  few  crystals  of  ammonium  carbonate  and  then  ignited 
until  the  stannic  sulphide  is  completely  converted  into  the  white  oxide 
and  weighed  :  Sn02  x  0-7881  =  Sn. 

1  In  presence  of  copper  it  is  convenient  to  use  sodium  sulphide,  but  in  such  case 
the  rapid  determination  of  the  tin  with  rotating  electrodes  cannot  be  carried  out. 

2  For  the  coppering  of  the  electrode,  see  p.  225.     For  the  subsequent  tinning,  the 
following  solution  is  employed  :   3-4  grams  of  stannic  ammonium  chloride  are  dissolved 
in  150  c.c.  of  cold  water  to  which  are  added  150  c.c.  of  saturated  ammonium  bioxalate 
solution.     The  cathode  is  immersed  in  this  solution  and  the  current  passed  for  some 
minutes  :    ND100  =0-2-0-5  ampere. 


256  TIN-PLATE 

B.  DETERMINATION  OF  THE  LEAD.  i.  Electrolytically.  The  lead  and 
iron  sulphides  (see  p.  255)  are  washed  with  water  containing  a  little  ammo- 
nium or  sodium  sulphide,  and  the  filter  and  precipitate  heated  to  boiling 
with  15-20  c.c.  of  nitric  acid  (D  1-2)  in  a  small  covered  beaker.  The  solution 
is  decanted  through  a  filter  and  the  residue  boiled  with  20-30  c.c.  of  the 
following  mixture,  which  dissolves  also  any  small  amount  of  lead  sulphate 
formed  by  oxidation  of  the  sulphide  :  40  c.c.  of  ammonia  (D  0-923),  67  c.c. 
of  nitric  acid  (D  1-332)  and  5  grams  of  copper  nitrate.  The  liquid  is  filtered, 
the  filter  washed  with  hot  water  acidified  with  nitric  acid,  and  the  filtrate 
made  up  to  about  200  c.c.  and  electrolysed  to  determine  the  lead  :  Winkler 
cathode  ;  matte  gauze  cylinder  anode  ;  ND  =0-3  amp.  ;  voltage,  1-8-2 
(see  also  Electrolytic  Determination  of  Lead  in  Ordinary  Brass). 

When  the  deposition  of  the  lead  is  complete,  the  anode  is  washed  with 
water  alone,  dried  at  200-220°  and  weighed  :  Pb02  X  0-866  =  Pb. 

2.  Gravimetrically .  The  lead  and  iron  sulphides  (see  i,  p.  255)  on  the 
filter  are  well  washed  with  water  containing  a  little  ammonium  sulphide, 
dissolved  in  nitric  acid  (D  1-2)  and  filtered  by  decantation.  The  residue 
is  again  boiled  twice  with  nitric  acid  and  finally  washed  with  water  acidified 
with  nitric  acid.  The  nitric  acid  solution  is  evaporated  with  sulphuric  acid 
until  white  fumes  appear,  and  the  residue,  when  cold,  taken  up  in  water, 
the  lead  being  determined  as  sulphate  as  in  the  case  of  tin. 

2.  Determination  of  the  Lead  alone. — The  surface  of  the  tin-plate 
is  scraped  with  a  penknife  so  that  as  little  as  possible  of  the  metal  under- 
neath is  removed,  about  1-1-5  gram  of  thin  shavings  being  obtained  ;  any 
particles  of  iron  are  removed  with  a  magnet.  The  shavings  are  mixed  in 
a  covered  beaker  with  6  c.c.  of  fuming  nitric  acid  (D  1-5),  3  c.c.  of  water 
being  poured  carefully  down  the  side  of  the  beaker  so  that  the  two  liquids 
mix  slowly  and  the  action  proceeds  regularly.  At  the  end  of  the  action, 
the  liquid  is  heated  to  boiling,  diluted  with  50  c.c.  of  boiling  water  and, 
when  the  liquid  above  the  metastannic  acid  has  become  clear,  filtered  by 
decantation  through  a  dense  filter  and  washed  by  decantation  with  water 
slightly  acidified  with  nitric  acid. 

In  the  filtrate  the  lead  is  determined  either  electrolytically  or  gravi- 
metrically  by  the  methods  given  for  the  analysis  of  alloys  of  lead  and  tin 
(see  p.  259).  When  the  lead  is  separated  as  peroxide  or  sulphate,  the  iron 
unavoidably  present  is  determined  in  the  residual  liquid  by  precipitating 
with  ammonium  chloride  and  ammonia.  Deduction  of  the  weight  of  iron 
found  from  the  total  weight  of  the  shavings  gives  the  amount  of  lead-tin 
alloy  taken  for  analysis,  and  to  this  the  quantity  of  lead  found  is  referred. 


Good  tin-plate  should  exhibit  a  clean,  smooth  surface  without  spots  or 
bubbles  and  with  a  uniformly  thick  layer  of  tin.  It  should  have  at  least  0-25-0-3 
gram  of  tin  per  sq.  dm.  (the  best  qualities  have  o-6-o-7  gram  per  sq.  dm.),  and 
the  tin  used  should  not  contain  more  than  i%  of  lead. 


PHOSPHOR-TIN   (TIN   PHOSPHIDE)  257 

PHOSPHOR-TIN 
(Tin  phosphide) 

The  analysis  of  phosphor-tin,  which  is  used  especially  for  the  preparation 
of  phosphor-bronzes,  includes  : 

1.  Determination  of  the  Phosphorus.1 — The  alloy  is  treated  with 
hydrochloric  acid  and  the  phosphorus  thus  liberated  as  hydrogen  phosphide, 
which  is  oxidised  with  bromine  water  and  determined  as  phosphoric  acid. 

Apparatus.  A  flask  of  about  500  c.c.  capacity  furnished  with  a  stopper 
through  which  pass  (i)  a  tapped  funnel  for  the  introduction  of  the  hydro- 
chloric acid  and  (2)  two  tubes  bent  at  right  angles,  one  reaching  almost 
to  the  bottom  of  the  vessel  and  serving  for  the  introduction  of  a  stream 
of  carbon  dioxide  into  the  apparatus,  and  the  other  to  collect  the  gas  evolved 
during  the  reaction.  The  latter  tube  communicates  with  three  absorption 
bottles,  two  containing  bromine  water  and  a  small  quantity  of  bromine 
(a  layer  some  millimetres  deep)  and  the  third  bromine  water  alone. 

Procedure.  2-5  grams  of  the  alloy  in  small  fragments  are  introduced 
into  the  flask  and  the  latter  stoppered  and  connected  with  the  washing 
bottles,  a  current  of  carbon  dioxide  being  passed  for  about  five  minutes  to 
expel  the  air.  From  50  to  100  c.c.  of  concentrated  hydrochloric  acid  are 
then  added,  little  by  little,  and  when  the  attack  is  complete  the  liquid  is 
heated  to  boiling  and  a  current  of  carbon  dioxide  again  passed  to  drive 
out  the  products  of  the  reaction.  The  contents  of  the  three  bottles  are 
washed  into  a  beaker,  the  excess  of  bromine  eliminated  by  boiling  and  the 
phosphoric  acid  precipitated  either  (i)  as  magnesium  ammonium  phosphate 
which,  after  standing,  is  filtered  off,  dried,  ignited  strongly  and  weighed  : 
Mg2P2O7  X  0-2787  =  P,2  or  (2)  with  ammonium  molybdate  (see  Iron,  4). 

2.  Determination   of  the   Tin. — The   hydrochloric   acid   solution   is 
collected  in  a  500  c.c.  measuring  flask  and  made  up  to  volume.     An  aliquot 
part,  corresponding  with  0-5-0-75  gram  of  the  sample,  is  rendered  alkaline 
with  ammonia,  the  precipitate  redissolved  by  addition  of  a  little  oxalic  acid 
and  the  liquid  boiled  for  a  short  time  with  25  c.c.  of  hydrochloric  acid,  25 
grams  of  ammonium  oxalate  and  a  few  drops  of  hydrogen  peroxide,  made 
up  to  about  250  c.c.  and  electrolysed  at  40-50°  to  determine  the  tin  (see 
Electrolytic  Determination  of  Tin  in  Ordinary  Bronzes). 

*** 

Commercial  phosphor-tin  or  tin  phosphide  usually  contains  about  4%  of 
phosphorus.  The  brand  marked  N.o  contains  about  5%  P  and  N.I,  2-5%. 
Other  products,  however,  contain  only  i%  or  even  less. 

1  W.  Gemmell  and  S.  L.  Archbutt,  Journ.  Soc.  Chem.  Industry,  1908,  XXVII,  p. 
427. 

2  If  the  sample  contains  arsenic,  magnesium  ammonium  arsenate  is  precipitated 
with  the  magnesium  ammonium  phosphate.     In  this  case  the  weighed  precipitate  is 
redissolved  in  hydrochloric  acid,  the  solution  reduced  with  sulphur  dioxide  and  the 
arsenic  precipitated  with  hydrogen  sulphide, 

A.C.  17 


258  ALLOYS   OF   LEAD  AND  TIN 

ALLOYS    OF    LEAD    AND    TIN 

The  lead-tin  alloys  are  used  for  soldering  and  for  many  other  purposes, 
such  as  making  ornamental  articles,  statuettes,  toys,  tubes  for  paints  and 
perfumery,  tin-foil,  etc. 

In  these  alloys,  the  essential  determinations  are  those  of  the  lead  and 
tin  (see  i).  Sometimes,  however,  for  special  products,  the  determination 
of  the  lead  alone  or  of  the  tin  alone  is  of  interest  (see  2),  whilst  in  other 
cases,  determination  of  the  impurities  (Cu,  Sb,  As,  etc.)  is  desired  (see  White 
Metals). 

1.  Determination  of  the  Lead  and  Tin. — About  i  gram  of  the  alloy 
as  filings  is  treated  in  a  covered  beaker  with  6  c.c.  of  fuming  nitric  acid 
(D  =  1-5)  and  3  c.c.  of  water  then  poured  carefully  down  the  side  of  the 
beaker  so  that  the  two  liquids  mix  slowly  and  the  action  proceeds  slowly 
and  regularly.  When  the  action  is  complete,  the  liquid  is  heated  to  boiling, 
diluted  with  50  c.c.  of  boiling  water,  and,  when  the  liquid  above  the  pre- 
cipitated metastannic  acid  has  become  clear,  filtered  by  decantation  through 
a  close  filter-paper.  The  precipitate  is  washed  by  decantation  with  water 
slightly  acidified  with  nitric  acid,  collected  on  the  filter,  washed  with  hot 
water  x  and  treated  as  in  B.  The  filtrate  is  utilised  as  in  A. 

A.  DETERMINATION  OF  THE  LEAD. 

1.  Electrolytically .     The  filtrate  is  made  up  to  volume  and  an  aliquot 
part,  containing  about  0-2-0-25  gram  of  lead,  is  treated  with  1-2  grams 
of  pure  copper  dissolved  in  10-15  c.c.  of  nitric  acid,  diluted  to  200-250  c.c., 
and  electrolysed  at  the  ordinary  temperature  :   Winkler  anode  )  cylindrical 
gauze  cathode  ;   ND100  =  0-3  amp.  ;  voltage  =  2-2-2  ;   and  duration,!  10-15 
hours. 

When  by  raising  the  level  of  the  liquid  the  deposition  of  the  lead  is  found 
to  be  complete — even  although  copper  may  still  remain  in  solution— the 
electrolytic  beaker  is  replaced  by  another  filled  with  distilled  water,  the 
current  being  maintained.  After  some  time  the  anode  coated  with  lead 
peroxide  is  detached,  washed  with  water  alone  and  dried  at  200-220°.  The 
factor  for  converting  weight  of  peroxide  into  that  of  lead  is  0-866,  0-865 
or  0-8635  according  as  the  amount  of  the  peroxide  is  less  than  o-i  gram, 
between  o-i  and  0-3  gram,  or  above  0-3  gram  (Classen). 

2.  Gravimetrically .     The  filtrate  is  evaporated  in  presence  of  3-4  c.c. 
of  cone,  sulphuric  acid  until  white  fumes  appear.     When  cold,  the  liquid 
is  taken  up  with  50  c.c.  of  water,  heated  gently  and  stirred,  allowed  to  cool 
and  treated  with  15  c.c.  of  95%  alcohol.     After  1-2  hours,  the  lead  sulphate 
is  collected  in  a  Gooch  crucible  and  weighed  (see  Gravimetric  Determination 
of  Lead  in  Ordinary  Brass). 

B.  DETERMINATION  OF  THE  TIN. 

i.  Electrolytically.     The  metastannic  acid  precipitate  with  the  filter- 
When  fuming  nitric  acid  is  used,  the  metastannic  acid  separating  is  practically 
free  from  lead  (Busse  :   Zeilschr.  analyt.  Chem.,  1878,  XVII,  p.  53).     If  it  is  desired  to 
determine  the  minimal  quantities  of  lead  retained  in  the  metastannic  acid,  the  methods 
indicated  for  the  determination  of  tin  in  ordinary  bronzes  (see  p.  232)  may  be  used. 


ALLOYS  OF  LEAD   AND  TIN  259 

paper  is  treated  in  a  small  beaker  with  2-3  c.c.  of  10%  sodium  hydroxide 
solution  and  10-15  c.c.  of  sodium  sulphide  (D  1-225),  the  remaining  pro- 
cedure being  that  given  for  the  electrolytic  determination  of  tin  in  ordinary 
bronze  (see  p.  232). 

2.  Gravimetrically .  The  filtered  and  washed  metastannic  acid  precipi- 
tate is  dried  at  100°  and  removed  as  far  as  possible  from  the  filter  to  a  tared 
porcelain  crucible.  The  filter-paper  is  incinerated  in  a  dish,  the  ash  added 
to  the  precipitate,  the  whole  moistened  with  a  few  drops  of  nitric  acid,  the 
excess  of  acid  evaporated  and  the  residue  ignited  at  first  with  an  ordinary 
flame  and  afterwards  by  means  of  the  blowpipe,  and  weighed  1 :  SnO2  X 
07881  =  Sn. 

2.  Determination  of  the  Lead  alone  or  of  the  Tin  alone. 

1.  LEAD  ALONE.     This  is  of  interest  in  some  tin-lead  alloys  composed 
mainly  of  tin,  such  as  solder  for  culinary  utensils  and  the  like. 

In  a  covered  electrolytic  beaker  of  350  c.c.  capacity,  1-3  grams  of  the 
alloy  as  filings  are  treated,  according  to  the  amount  of  alloy  taken,  with 
6-20  c.c.  of  fuming  nitric  acid  (D  1-5),  3-9  c.c.  of  water  being  then  allowed 
to  flow  slowly  down  the  wall  of  the  beaker.  When  the  attack  of  the  metal 
is  complete,  the  liquid  is  boiled  for  a  short  time,  diluted  to  about  250  c.c. 
and  thoroughly  mixed  with  2-3  grams  of  copper  nitrate  or  with  1-1-5  gram 
of  pure  copper  dissolved  in  a  little  nitric  acid,  the  metastannic  acid  being 
allowed  to  settle  and  the  liquid,  without  filtering,  electrolysed  to  determine 
the  lead  :  Winkler  cathode  ;  matte  gauze  cylinder  anode  ;  ND100.  0-3  amp. 
and  voltage,  2-2-2.  The  cathode  should  touch  the  bottom  of  the  beaker, 
whilst  the  anode  should  not  reach  to  within  about  I  cm.  from  the  layer  of 
precipitate  (for  the  factor,  Pb  :  Pb02,  see  p.  258).  In  this  way,  even  the 
small  quantities  of  lead  held  by  the  metastannic  acid  may  be  liberated  by 
the  current. 

2.  TIN  ALONE.     In  other  types  of  alloy,  consisting  essentially  of   lead 
(sometimes  hard  lead)   with  small  quantities  of  tin   (0-5-15%),  such  as 
are  used  for  tubes  for  perfumery,  colours,  etc.,  wires  for  electric  valves, 
etc.,  it  is  of  interest  to  determine  the  tin  alone. 

From  2  to  3  grams  of  the  sample  in  filings  or  clippings  are  treated  with 
20-25  c.c.  of  boiling  cone,  sulphuric  acid  and,  when  the  action  is  at  an  end, 
the  liquid  diluted  somewhat.  When  the  liquid  is  cold,  5-6  grams  of  tartaric 
acid  are  dissolved  in  it  and  the  whole  transferred  to  a  100  c.c.  measuring 
flask,  made  up  to  volume,  and  filtered  through  a  dry  filter.  The  tin  is 
determined  in  50  c.c.  of  the  filtrate  in  the  way  given  for  the  determination 
of  tin  in  hard  lead  (see  p.  248). 


* 
*  * 


The  composition  of  solder  varies  widely  with  the  metals  to  be  soldered  and 
with  the  resistance  to  be  offered  to  mechanical  action,  heat,  etc.  Solders  for 
coarse  work  contain  about  30%  of  tin  and  70%  of  lead,  whilst  those  for  soft 
soldering  of  small  articles  contain  about  70%  of  tin  and  30%  of  lead  ;  in  some 
cases  as  much  as  90%  or  more  of  tin  are  present.  The  most  readily  fusible 
alloy  (183°)  contains  37%  of  lead  and  63%  of  tin. 

1  In  this  way  any  antimony  present  is  calculated  as  tin,  For  the  separation  of 
tin  from  antimony,  see  White  Metals. 


26o  WHITE  METAL 

TIN-FOIL 

Tin-foil,  properly  so  called,  should  consist  of  thin  sheets  of  pure  tin 
and  is  hence  analysed  as  described  for  tin.  Often,  however,  it  is  formed 
of  lead  and  tin,  or  of  lead,  antimony  and  tin,  and  in  some  cases  is  tinned 
to  obtain  the  shining  white  colour  of  tin.  With  these  last  two  types  of 
tin-foil,  the  most  important  determination  is  that  of  the  tin,  this  being 
effected  as  for  the  tin  alone  in  lead-tin  alloys  (see  Alloys  of  Lead  and  Tin, 
p.  258).  A  complete  analysis  may  be  carried  out  by  the  method  indicated 
for  the  analysis  of  lead-tin  alloys,  when  these  are  the  only  constituent  metals, 
or  by  that  given  for  white  metal  in  the  case  of  an-  alloy  of  lead,  antimony 
and  tin. 

If  the  foil  is  tinned  externally,  the  coating  must  be  removed  in  order 
that  the  quantity  of  tin  actually  present  in  the  alloy  may  be  determined. 
If  the  foil  is  moderately  thick,  the  surface  layer  may  be  removed  mechani- 
cally from  the  two  faces  and  the  quantitative  determination  made  on  the 
sample  thus  prepared.  If,  however,  the  foil  is  too  thin  and  weak  to  be 
scraped,  the  surface  tin  is  removed  by  means  of  sodium  hydroxide  solution 
and  hydrogen  peroxide,  which,  at  the  proper  concentration,  easily  attacks 
and  dissolves  the  layer  of  tin,  whereas  the  tin  in  the  alloy  is  acted  on  either 
not  at  all  or  but  slightly.  The  conditions  to  be  observed  are  as  follows  i  : 

From  5  to  6  grams  of  the  foil  are  freed  from  grease  by  treatment  with 
ether,  cut  into  squares  of  about  i  cm.  side  and  heated  in  a  200  c.c.  flask 
with  20  c.c.  of  10%  sodium  hydroxide  to  40°,  6-8  drops  of  30%  (100  volume) 
hydrogen  peroxide  being  then  added  with  continual  shaking.  The  surface 
tin  passes  rapidly  into  solution  and  as  soon  as  the  lead-grey  colour  assumed 
by  the  pieces  of  metal  indicates  that  this  process  is  complete,  the  alkaline 
solution  is  decanted  off  and  the  residue  washed  repeatedly  with  water, 
alcohol  and  ether  successively  and  dried  at  60-70°.  The  foil  being  thus 
freed  from  the  surface  tin,  the  quantitative  determination  of  the  components 
of  the  alloy  is  carried  out  by  the  methods  indicated  above. 

WHITE    METAL 

This  includes  many  types  of  alloys  with  a  basis  of  tin-antimony,  lead- 
antimony  or  lead-tin-antimony,  together  with  small  quantities  of  copper 
and  sometimes  zinc  and  iron  (rarely  mercury  and  arsenic),  used  as  antifriction 
metals,  type  metal,  metal  for  fittings,  etc.  The  composition,  and 
therefore  the  analytical  methods  to  be  used,  vary  with  the  purpose  of 
the  metal.  Three  groups  may  be  distinguished  : 

(1)  Alloys  with  a  basis  of  tin  (70-85%)  and  antimony  (10-15%),  with 
a  little  copper  (5-10%)  and  lead  (0-5-2%),  and  perhaps  zinc  and  iron. 

(2)  Alloys  with  a  basis  of  lead  (60-80%),  antimony  (10-15%)  and  tin 
(10-25%),  with  a  little  copper  (0-5-1%)  and  perhaps  zinc,  iron  and  arsenic. 

(3)  Alloys  with  a  basis  of  lead  (75-90%)  and  antimony  (10-25%),  with 
a  small  quantity  of  tin  and  copper  (0-5-2%). 

1  Belasio  :  "  Determination  of  Tin  in  Foil  of  Lead,  Tin  and  Antimony  Tinned  Ex- 
ternally" (Ann,  Labor.  Chim,  Gdbette,  VI,  p.  231). 


WHITE  METAL  261 

For  each  group  the  method  of  analysis  will  be  described  later,  but 
since  for  certain  purposes  only  the  content  of  copper  or  tin  is  of  interest, 
a  general  method  is  given  which  permits  of  the  direct  and  moderately  rapid 
determination  of  each  of  these  elements. 

1.  Direct  Determination  of  the  Copper.1 — In  a  200  c.c.  measuring 
flask,  5  grams  of  the  alloy  are  heated  gently  with  20-25  c.c.  of  nitric  acid 
(D  1-2)  *   when  the  action  is  complete,  the  nitrous  vapours  are  eliminated 
by  short  boiling  and  the  liquid  cooled,  treated  with  3  c.c.  of  cone,  sulphuric 
acid,  again  cooled,  diluted  somewhat,  rendered  alkaline  with  ammonia, 
treated  with  15-20  c.c.  of  10%  sodium  phosphate  solution  and  made  up 
to  volume  and  mixed.     After  standing,  the  liquid  is  filtered  through  a 
dry  filter  and  100  c.c.  of  the  filtrate  neutralised  with  nitric  acid,  treated 
with  6  c.c.  of  cone,  nitric  acid  and  20  c.c.  of  10%  sulphuric  acid,  and  elec- 
trolysed :    Winkler  cathode  J    spiral  Winkler    anode  ;    ND100  =  0-2  amp.  ; 
voltage  =  1-8-2-2  ;  and  duration,  10-12  hours. 

When  the  copper  is  completely  deposited,  the  electrolytic  beaker  is 
replaced  by  another  small  beaker  full  of  distilled  water  acidified  slightly 
with  sulphuric  acid,  the  cathode  being  detached  after  some  time,  washed 
with  water,  alcohol  and  ether,  dried  at  70°  and  weighed.  (Weight  of  coppe: 
found)  X  40  =  percentage  of  copper  in  the  sample. 

If  the  alloy  contains  arsenic,  the  copper  deposited  may  have  a  brown 
colour.  In  this  case  the  deposit  is  dissolved  in  5-6  c.c.  of  nitric  acid  and 
the  liquid  diluted  and  again  electrolysed. 

2.  Direct  Determination  of  the  Tin. — According  to  the  supposed 
tin  content,  1-3  grams  of  the  alloy  in  fine  filings  are  treated  with  15-20  c.c. 
of  concentrated,  boiling  sulphuric  acid,  the  subsequent  procedure  being 
that  indicated  for  the  direct  determination  of  tin  in  hard  lead  (seep.  247). 

1.  Alloys  with  a  Tin -Antimony  Basis 

These  alloys  usually  contain  70-85%  Sn,  10-15%  Sb,  5-10%  Cu,  0-5- 
2%  Pb,  with  possibly  zinc  and  iron.  Their  complete  analysis  is  carried  out 
as  follows  : 

A.  Electrolytically.2 — In  a  conical  flask  covered  with  a  small  funnel, 
0-5-1  gram  of  the  alloy  in  turnings  or  filings  is  treated  with  the  least  possible 
quantity  of  aqua  regia  (10-15  c.c.).  When  the  action  is  over,  10-15  c.c. 
of  water  containing  in  solution  2-3  grams  of  tartaric  acid  are  added  and 
the  liquid  made  slightly  alkaline  with  concentrated  caustic  soda  solution 
and  treated  with  a  further  quantity  of  2  grams  of  sodium  hydroxide  and 
10-15  c.c.  of  sodium  sulphide  solution  (D  1-225).  The  liquid  is  heated  on 
a  water-bath  with  frequent  shaking  and  after  about  15  minutes — when 
the  sulphides  insoluble  in  sodium  sulphide  have  settled — filtered  by  decan- 
tation  through  a  filter  moistened  with  sodium  sulphide  into  a  tared  Classen 
dish.  The  residue  is  washed  by  decantation  five  or  six  times  with  tepid 
sodium  sulphide  (70-80  c.c.  in  all)  and  then  once  with  a  very  little  hot 
water  containing  a  few  drops  of  sodium  sulphide.  The  filtrate  contains 

1  Belasio  :    Ann.  Labor.  Chim.  Gdbelle,  VI,  p.  284. 
z  Belasio:    Ann.  Labor.  Chim.  Gabelle,  VI,  p.  217. 


262  WHITE  METAL 

all  the  antimony  and  tin  (see  i,  2)  and  the  residue  insoluble  in  sodium 
sulphide  the  copper  and  lead  and  also  any  zinc  and  iron  present  (see  3,  4). 

1.  DETERMINATION  OF  THE  ANTIMONY.     The  nitrate  is  treated  with 
7-8  grams  of  pure  potassium  cyanide  (precipitated  by  alcohol)  and  elec- 
trolysed at  the  ordinary  temperature  to  determine  the  antimony  :    Classen 
capsule  cathode  ;   disc  or  spiral  anode  ;   ND100  =  o-i5-o-i7  amp.  ;   voltage 
=  1-1-2  ;  and  duration  =  15-17  hours. 

When  the  whole  of  the  antimony  is  deposited,  the  electrolyte  is  poured 
into  a  J-litre  flask  and  the  capsule  and  disc  (or  spiral)  washed  with  a  little 
water  which  is  also  poured  into  the  flask.  The  capsule  is  then  thoroughly 
washed  with  water,  alcohol  and  ether,  dried  at  70°  and  weighed. 

2.  DETERMINATION  OF  THE  TIN.     The  alkaline  liquid  freed  from  anti- 
mony is  acidified  faintly  with  dilute  sulphuric  acid  (i  vol.  acid,  2  vols.  water), 
the  flask  being  kept  under  a  hood,  covered  with  a  funnel  and  shaken.     The 
liquid  is  then  boiled  for  some  time  to  expel  the  bulk  of  the  hydrogen  sulphide 
and  cyanogen  compounds,  left  on  a  boiling  water-bath  for  about  15  minutes 
and  filtered    through  a  filter-paper  moistened  with  ammonium  sulphate 
solution,  the  precipitate  being  washed  with  a  little  hot  water  saturated 
with  hydrogen  sulphide. 

The  filter  and  precipitate  are  then  heated  to  boiling  in  a  small  covered 
beaker  with  20  c.c.  of  cone,  hydrochloric  acid  and  15-20  c.c.  of  10%  ammo- 
nium chloride  solution,  a  few  crystals  of  potassium  chlorate  being  sub- 
sequently added  to  complete  the  action.  The  liquid  is  then  diluted  with 
15-20  c.c.  of  boiling  water,  shaken  and  filtered  into  a  ^-litre  flask,  washing 
with  hot  water  acidified  with  hydrochloric  acid.  The  filtrate  is  rendered 
slightly  alkaline  with  ammonia,  treated  with  5  grams  of  oxalic  acid  and 
heated  a  little,  5  grams  of  ammonium  oxalate  being  added  to  the  clear 
solution,  which  is  then  made  up  to  150-200  c.c.  and  subjected  to  a  moderate 
current  of  hydrogen  sulphide  while  gently  boiling.  Under  these  conditions 
the  traces  of  copper  dissolved  in  the  sodium  sulphide  and  also  any  arsenic 
present  are  precipitated.  After  about  an  hour  the  liquid  is  allowed  to  cool 
somewhat  in  the  stream  of  hydrogen  sulphide  and  is  then  filtered  into  a 
| -litre  beaker  and  the  filter  washed  with  a  hot  1%  oxalic  acid  solution 
saturated  with  hydrogen  sulphide.  The  filtrate  is  boiled  with  25  c.c.  of 
cone,  hydrochloric  acid  and  12-14  grams  of  ammonium  oxalate  for  about 
15  minutes  to  expel  the  hydrogen  sulphide,  allowed  to  cool  a  little,  treated 
with  3-4  drops  of  30%  hydrogen  peroxide,  boiled  again,  cooled  to  about 
50°  and,  without  removal  of  any  suspended  sulphur,  electrolysed  to  deter- 
mine the  tin  (see  Electrolytic  Determination  of  Tin  in  Ordinary  Bronzes) . 

3.  DETERMINATION  OF  THE  COPPER  AND  LEAD.    The  filter  and  hydrogen 
sulphide  precipitate  (see  2)  are  incinerated  in  a  small  dish  and  then  ignited, 
the  residue  being  dissolved  in  2-3  c.c.  of  nitric  acid. 

The  sulphides  remaining  undissolved  in  the  sodium  sulphide  (see  A) 
are  dissolved  in  10-15  c.c.  of  boiling  nitric  acid  (D  1-2),  filtered  by  decan- 
tation,  the  residue  being  treated  again  twice  with  nitric  acid  and  the  united 
nitric  acid  solutions  (including  that  from  the  hydrogen  sulphide  precipitate) 
used  for  determining  the  lead  and  copper  as  well  as  any  zinc  and  iron  present. 

If  the  copper  preponderates  over  the  lead,  as  is  usual  with  alloys  of  this 


WHITE  METAL  263 

group — which  scarcely  contain  impurities  of  lead — the  copper  and  lead  are 
at  once  determined  simultaneously  (see  Electrolytic  Determination  of 
Copper  and  Lead  in  Ordinary  Brass).  If,  however,  the  lead  is  in  the  pre- 
ponderance, it  is  separated  and  determined  as  sulphate,  the  copper  being 
then  determined  in  the  nitrate  (see  Determination  of  Lead  and  Copper  in 
Complex  Brasses). 

4.  DETERMINATION  OF  THE  IRON  AND  ZINC.    The  liquid  from  which  the 
lead  and  copper  have  been  separated  is  used  for  the  determination  of  the 
iron  and  zinc  as  in  ordinary  brasses. 

5.  DETERMINATION  OF  THE  ARSENIC.     See  Determination  of  Arsenic  in 
Tin. 

B.  Gravimetrically. — 2  grams  of  the  sample  are  acted  on  with 
the  least  possible  quantity  of  aqua  regia  at  a  gentle  heat  on  a  water-bath. 
When  the  action  is  complete,  the  liquid  is  diluted  with  10-15  c.c.  of  water 
containing  2-3  grams  of  tartaric  acid  in  solution,  then  rendered  faintly 
alkaline  with  sodium  hydroxide  solution  and  treated  with  colourless  sodium 
sulphide  in  very  slight  excess.  The  liquid  is  heated  on  a  water-bath  with 
occasional  shaking  until  the  precipitate  has  settled  and  is  then  filtered  by 
decantation,  hot  water  containing  a  little  sodium  sulphide  being  used  for 
washing.  The  nitrate,  containing  tin  and  antimony,  is  analysed  according 
to  i  and  the  precipitate,  containing  lead,  copper,  etc.,  according  to  2. 

i.  DETERMINATION  OF  THE  TIN  AND  ANTIMONY.  The  filtrate  is  made 
up  to  i  litre  and  200  c.c.  treated  in  a  |-litre  flask  with  6  grams  of  potassium 
hydroxide,  3  grams  of  tartaric  acid  and  slowly  and,  if  necessary,  with  cooling, 
sufficient  30%  hydrogen  peroxide  to  decolorise  the  solution,  that  is,  to 
transform  the  sodium  sulphide  completely  into  sulphate.  The  liquid  is 
boiled  for  some  time  to  expel  excess  of  hydrogen  peroxide,  allowed  to  cool, 
neutralised  with  saturated  oxalic  acid  solution  and  treated  with  5  grams 
of  solid  oxalic  acid,  diluted  to  about  250  c.c.  and  subjected  at  the  boiling 
point  to  a  moderate  current  of  hydrogen  sulphide  for  about  an  hour.  The 
solution  is  then  allowed  to  cool  somewhat  in  the  stream  of  hydrogen  sulphide 
and  the  antimony  sulphide  filtered  off  and  washed  with  i%  oxalic  acid 
solution  saturated  with  hydrogen  sulphide. 

Since  this  antimony  sulphide  may  contain  small  quantities  of  tin,  it  is 
dissolved  in  a  mixture  of  10-15  c.c.  of  cone,  hydrochloric  acid  and  10-15 
c.c.  of  10%  ammonium  chloride  solution,  a  few  crystals  of  potassium  chlorate 
being  added  when  the  mixture  begins  to  boil.  After  dilution  with  water, 
the  liquid  is  filtered,  made  slightly  alkaline  with  ammonia,  treated  with 
5  grams  of  oxalic  acid,  diluted  to  150  c.c.  and  the  boiling  liquid  again  treated 
with  hydrogen  sulphide. 

(a)  Determination  of  the  tin.  The  two  filtrates  are  united,  rendered 
distinctly  alkaline  with  ammonia,  acidified  with  acetic  acid,  and  a  current 
of  hydrogen  sulphide  passed  through  the  solution  for  about  three  hours. 
After  a  rest  of  about  30  minutes  on  a  water-bath  to  facilitate  the  separation 
of  the  precipitate,  the  latter  is  filtered  off  and  washed  with  hydrogen  sulphide 
solution  containing  a  little  ammonium  sulphate.  The  tin  sulphide  thus 
obtained  is  dried  at  120°,  transformed  by  ignition  into  the  oxide  and  the 
latter  weighed  :  SnO2  X  07881  =  Sn. 


264  WHITE   METAL 

(b)  Determination  of  the  antimony.  The  antimony  sulphide  on  the 
filter  (see  i)  is  dissolved  in  a  little  yellow  ammonium  sulphide,  the  solution 
evaporated  in  a  tared  porcelain  crucible,  the  residue  treated  carefully,  to 
avoid  spurting,  with  nitric  acid  and  the  liquid  evaporated  to  dryness.  The 
treatment  with  nitric  acid  is  repeated  twice  to  ensure  the  complete  oxidation 
of  the  sulphur,  the  residue  being  ignited  and  weighed  :  Sb2O4  x  0-7898  = 
Sb. 

2.  DETERMINATION  OF  THE  LEAD,  COPPER,  IRON  AND  ZINC.  The  sul- 
phides remaining  undissolved  in  sodium  sulphide  are  dissolved  in  nitric 
acid  (D  1-2),  the  filtered  solution  treated  with  a  little  sulphuric  acid  and 
evaporated  until  white  fumes  appear,  the  subsequent  procedure  being  as 
indicated  for  the  gravimetric  determination  of  lead,  copper,  iron  and  zinc 
in  ordinary  brass. 

2.  Alloys  with  a  Lead -Antimony -Tin  Basis 

These  alloys  usually  contain  60-80%  Pb,  10-15%  Sb,  10-25%  Sn,  a 
little  copper  and  possibly  zinc,  iron,  arsenic.  The  complete  analysis  is 
carried  out  as  follows  : 

A.  Electrolytically. — i  gram  of  the  sample  in   fine  filings  is  treated 
with  20  c.c.  of  cone,  hydrochloric  acid  and  2-3  c.c.  of  cone,  nitric  acid  and 
left  overnight  in  order  that  the  action  may  proceed  slowly  but  completely. 

1.  DETERMINATION  OF  THE  LEAD.     The  acid  solution  is  treated  with 
10  vols.  of  absolute  alcohol  (220-230  c.c.),  cooled  and  after  a  suitable  rest 
(3-4  hours) — when  the  bulk  of  the  lead  chloride  has  separated  (only  a  few 
milligrams,  to  be  estimated  later,  remain  in  solution) — filtered  through  a 
tared  Gooch  crucible,  washed  with  alcohol  to  a  neutral  reaction,  dried  at 
100°  and  weighed  :    PbQ2  X  07447  =  Pb. 

2.  DETERMINATION  OF  THE  TIN,  ANTIMONY,  COPPER,  IRON  AND  ZINC. 
The  alcoholic  solution,  freed  from  lead  chloride,  is  evaporated  with  2-3 
grams  of  tartaric  acid  until  the  alcohol  is  completely  expelled,  then  made 
slightly  alkaline  with  concentrated  sodium  hydroxide  solution  and  treated 
with  2  grams  of  sodium  hydroxide  and  15-20  c.c.  of  sodium  sulphide  solu- 
tion (D  =  1*225).     After  being  heated  for  about  15  minutes  on  a  water- 
bath,  the  liquid  is  filtered  into  a  Classen  capsule,  the  precipitate  being 
washed  five  or  six  times  with  sodium  sulphide  solution  (60-70  c.c.   in  all) 
and  then  with  hot  water  containing  a  few  drops  of  sodium  sulphide.     The 
filtrate  contains  the  tin  and  antimony  and  the  insoluble  residue  the  copper, 
traces  of  lead  dissolved  as  chloride,  and  any  iron  and  zinc  present. 

For  the  electrolytic  determination  of  these  elements,  the  method  pre- 
viously described  (see  i,A,  p.  261)  x  is  followed. 

B.  Gravimetrically. 

i.  DETERMINATION  OF  THE  LEAD,  i  gram  of  the  sample  is  attacked 
with  aqua  regia  and  the  lead  separated  as  chloride  under  the  conditions 
described  above  (see  A). 

1  If  the  copper  is  present  in  very  small  amount,  it  is  more  convenient  to  make 
the  direct  determination  (see  p.  261)  and  in  such  case,  when  the  lead  in  solution  as 
chloride  is  to  be  determined,  it  is  advisable  to  add  a  little  copper  nitrate  to  the  electrolyte. 


WHITE  METAL 


265 


2.  DETERMINATION  OF  THE  TIN,  ANTIMONY,  COPPER,  IRON  AND  ZINC. 
The  alcoholic  solution  is  evaporated  with  2-3  grams  of  tartaric  acid  until 
the  alcohol  is  completely  expelled,  the  residue  being  taken  up  in  water 
and  the  liquid  made  faintly  alkaline  with  concentrated  sodium  hydroxide 
solution  and  treated  with  colourless  sodium  sulphide  solution  in  very  slight 
excess.  The  liquid  is  heated  on  the  water-bath  and  filtered,  the  subsequent 
procedure  being  that  for  the  gravimetric  analysis  of  alloys  with  a  tin-anti- 
mony basis  containing  a  little  copper  (see  p.  263). 

3.  Alloys  with  a  Lead -Antimony  Basis 

These  alloys  usually  contain  75-90%  Pb,  10-25%  Sb,  and  small  quan- 
tities of  tin  and  copper  (0*5-2%).  Their  complete  analysis  is  carried  out 
by  the  methods  given  for  hard  lead. 

*** 

White  metals  vary  in  composition  according  to  their  uses,  the  analytical 
results  for  some  of  the  commoner  types  being  as  follows  : 


TABLE    XXXIII 
Composition  of  White  Metal 


Type. 

Sn 

Pb 

Sb 

Cu 

Fe 

Zn 

Antifriction  metals  : 

Adopted  by  the  Italian  Railways   . 

83 

— 

II 

6 

— 

— 

„       French          ,, 

83-33 

•  — 

II-II 

5'55 

— 

— 

Russian                    •! 

90 

— 

8 

2 

— 

— 

( 

78-5 

— 

n-5 

IO 

— 

— 

,,             ,,       German        ,, 

83 

— 

ii 

6 

— 

— 

,,             ,,       Austrian       ,, 

82 

— 

12 

6 

— 

—  i 

English  white  bearing  metal 

76-7 

— 

15-5 

7-8 

— 

— 

Britannia  metal    

QO—  Q2 

8-0 

Ur>  to  •? 

•y^f      -y*. 

u     y 

r        .» 

Antifriction  and  fittings  metals  : 

Adopted  by  the  Italian  Railways  . 

M 

76 

10 

— 

— 

— 

French  Northern 

„             ,,           Railway 

12 

73 

15 

— 

— 

— 

,,       French    Eastern 

Railway  . 

12 

80 

8 

—  . 

— 

— 

by     certain    German 

Railways  . 

42 

42 

16 

—  . 

— 

-— 

Graphite  metal     

IS 

68 

17 

English  bearing  metal     .... 

*J 

53 

33 

-1/ 

10-6 

2-4 

— 

I 

American  antifriction  metal 

— 

78-4 

19-6 



0-7 

I 

Type  metal     

I  5-2^ 

TO—55 

2C—  -to 

trace 



"iJ          *} 

5 

*J          JJ 

80 

D    3 
IS 

trace 

Magnolia  metal    

*J 

83-5 

*s 

16-4 

"O  J 

78 

A"  T- 
21 

/ 

266  NICKEL 


NICKEL  AND  ITS  ALLOYS 

Nickel  is  largely  used  for  nickel  plating  and  for  coins  of  low  value,  and 
also  occurs  in  many  alloys. 

Descriptions  will  be  given  here  of  the  tests  to  be  made  on  commercial 
nickel  and  of  the  analysis  of  german  silver  and  the  like,  which  are  the  most 
important  nickel  alloys.  For  the  analysis  of  bronzes  containing  nickel,  see 
Nickel-bronzes. 

NICKEL 

The  more  common  determinations  involved  in  the  analysis  of  com- 
mercial nickel  are  those  of  copper,  cobalt,  iron,  manganese,  carbon,  sulphur, 
arsenic  and  silicon. 

10  grams  of  the  sample  are  dissolved  in  nitric  acid  and  evaporated  in 
presence  of  sulphuric  acid  until  dense  white  fumes  appear.  When  cold 
the  residue  is  treated  with  water  acidified  with  sulphuric  acid,  heated  to 
boiling,  filtered  and  washed  with  boiling  water  acidified  with  sulphuric 
acid.  The  residue  on  the  filter  is  treated  according  to  i  and  the  filtrate 
as  described  in  2,  3  and  4. 

1.  Determination  of  the  Silicon.— The  insoluble  residue,  consisting 
of  silica  and  possibly  metastannic  acid,  graphitic  carbon,  etc.,  is  dried, 
ignited  in  a  platinum  crucible,  weighed,  treated  with  hydrofluoric  acid 
and  a  few  drops  of  sulphuric  acid,  heated  to  expel  excess  of  acid,  again 
ignited,  cooled  and  weighed.     The  loss  in  weight  gives  the  silica  and  there- 
fore the  silicon  (see  Determination  of  the  Silicon  in  Iron). 

2.  Determination  of  the  Copper. — The  copper  is  precipitated  in  the 
filtrate  by  means  of  hydrogen  sulphide  and  is  then  determined  either  as 
oxide  or  electrolytically  by  dissolving  the  sulphide  in  nitric  acid  and  elec- 
trolysing the  solution. 

3.  Determination    of   the   Nickel    and    Cobalt. — (a)  Determination 
of  the  nickel.     The  filtrate  from  the  copper  sulphide  is  made  up  to  volume 
in  a  500  c.c.  measuring  flask,  and  100  c.c.  (corresponding  with  2  grams  of 
the  sample)  evaporated  to  dryness.     The  residue  is  taken  up  in  ammonia 
and  the  volume  then  made  up  to  100  c.c.  with  ammonia  (D  0-91),  5  grams 
of  ammonium  sulphate  being  dissolved  in  the  liquid  and  the  latter  elec- 
trolysed to  determine  the  nickel  and  cobalt  together  :    Winkler  cathode  ,' 
spiral  Winkler  anode  ;    ND100  =  0-7-1   amp.  ;   temperature,  ordinary,  and 
duration,  15-17  hours. 

The  cathode  is  subsequently  withdrawn,  washed,  dried  and  weighed, 
the  increase  in  weight  representing  nickel  and  cobalt  }  the  latter  is  then 
determined  separately  as  follows  : 

(b)  Determination  of  the  cobalt.1 — The  nickel  and  cobalt  deposited  on 
the  electrode  are  dissolved  in  nitric  acid,  the  solution  evaporated  to  dryness, 
the  residue  taken  up  in  a  little  water  and  evaporated  with  20  grams  of  pure 
ammonium  thiocyanate  until  the  salts  begin  to  crystallise  out,  and  the 
whole  washed  by  means  of  a  little  water  into  a  Rothe  extraction  apparatus. 

1  Ber.  deutsch.  Chem.  Gesell.,  1901,  XXXIV,  p.  2050. 


NICKEL  267 

It  is  here  shaken  with  50  c.c.  of  a  mixture  of  25  vols.  of  ether  with  i  vol. 
of  amyl  alcohol,  and  the  ethereal  layer— which,  in  presence  of  cobalt,  is 
blue — separated,  a  few  drops  of  concentrated  thiocyanate  solution  being 
used  for  washing.  The  extraction  with  the  ether-amyl  alcohol  mixture 
is  repeated  three  or  four  times,  until,  indeed,  it  remains  perfectly  colourless 
after  the  shaking.  The  various  solutions  containing  the  cobalt  are  then 
shaken  together  in  the  same  Rothe  apparatus  with  dilute  sulphuric  acid, 
into  which  the  cobalt  passes.  The  aqueous  layer  is  separated — washing 
with  a  little  dilute  sulphuric  acid — and  evaporated  to  dryness,  the  residue 
being  taken  up  in  a  little  water,  the  solution  made  faintly  ammoniacal  and 
any  traces  of  nickel  present  with  the  cobalt  precipitated  with  alcoholic 
dimethylglyoxime  solution.  The  precipitate  is  filtered  off,  the  nitrate 
evaporated  in  a  small  flask  with  nitric  and  sulphuric  acids  to  destroy  organic 
matter,  and  the  residual  liquid  placed  in  a  tared  crucible,  where  the  excess 
of  the  acids  is  expelled  and  the  remaining  cobalt  sulphate  then  weighed  : 
CoSO4  x  0-3804  =  Co. 

4.  Determination  of  the  Iron  and  Manganese. — The  400  c.c.  of 
solution  left  (8  grams  of  the  sample) — quite  free  from  hydrogen  sulphide 
— are  diluted  to  about  1-5  litre,  treated  with  hydrogen  peroxide  and  made 
alkaline  with  ammonia,  heated  and  then  left  at  rest  for  a  short  time  on  a 
water-bath,  the  supernatant  liquid  being  subsequently  siphoned  off  and 
the  precipitated  iron  and  manganese  oxides  collected  on  a  filter.     The 
precipitate  is  dissolved  in  a  little  hydrochloric  acid  and  the  precipitation 
with   hydrogen   peroxide   and   ammonia   repeated,   the  precipitate  being 
filtered  off  after  a  short  rest  on  the  water-bath,  washed  with  slightly  ammo- 
niacal water,  dried,  ignited  and  weighed. 

This  gives  the  ferric  and  manganese  oxides  together.     The  iron  alone 
is  then  determined  either  by  titration  or  by  separating  it  as  basic  acetate. 

5.  Determination    of   the    Carbon. — 3   grams    of   the   sample   are 
dissolved  on  the    water-bath  in  concentrated  copper-potassium  chloride 
solution,  the  carbonaceous  residue  being  collected  on  an  asbestos  filter, 
washed,  dried  and  burnt  in  a  current  of  oxygen  (see  Determination  of  Carbon 
in  Iron,  p.  168). 

6.  Determination  of  the  Sulphur. — 10  grams    of    the    sample  are 
dissolved  in  nitric  acids,  evaporated  several  times  with  hydrochloric  acid 
and  finally  taken  up  in  water  and  hydrochloric  acid  and  filtered.     In  the 
filtrate  the  sulphuric  acid  formed  by  oxidation  of  the  sulphur  is  precipitated 
with  barium  chloride  solution. 

7.  Determination  of  the  Arsenic. — From  10  to  20  grams  of  the 
sample  are  dissolved  in  nitric  acid,  the  solution  evaporated  with  sulphuric 
acid  until  the  nitric  acid  is  completely  expelled,  the  residue  dissolved  in 
water,  treated  with  5-10  grams  of  ferrous  sulphate  and  excess  of  hydro- 
chloric acid  and  the  arsenic  determined  by  distillation  (see  Determination 
of  Arsenic  in  Iron). 


*** 


Commercial  nickel  is  more  or  less  pure  according  to  the  processes  used  to 
obtain  it.  Of  the  impurities  which  it  may  contain  (Cu,  Co,  Fe,  Mn,  Sn,  Pb,  Sb, 
Ca,  Al,  C,  S,  Si,  SiO2,  P,  As),  the  most  injurious,  especially  if  the  metal  is  to 


268 


GERMAN   SILVER 


be  used  for  preparing  alloys,  are  sulphur,  arsenic  and  iron.  Cobalt,  which  is 
always  present  in  commercial  nickel  to  the  extent  of  1-2%,  copper,  which  does 
not  exceed  i%,  and  the  other  elements  mentioned  above,  provided  these  are 
present  only  in  small  proportions,  have  no  deleterious  effect  on  the  technical 
properties  of  the  metal. 

The  following  table  gives  the  properties  of  samples  of  nickel  of  different 
sources  (Lunge,  Hollard)  : 

TABLE    XXXIV 
Results  of  Analyses  of  Nickel 


CaO 

Origin. 

Ni 

Co 

Cu 

Mn 

Fe 

Sb 

As 

Pb 

S 

C 

Si 

SiO2 

Ala03 

and 
Alka- 

P 

lies 

German  Cubes  I  * 

97-08 

0-89 

0-15 

— 

1-22 

— 

— 

— 

trace 

O-02 

— 

o-35 

O-I2 

trace 

— 

98-21 

1-19 

0-07 

— 

O-25 

— 

— 

— 

trace 

trace 

— 

0-24 

trace 

trace 

— 

Granules  from  "  Konig  - 

warter  and  Ebell  " 

98-58 

o-75 

o  10 

— 

O-24 

— 

— 

— 

trace 

trace 

0-26 

— 

trace 

trace 

— 

English  cubes    .     . 

96-86 

1-26 

o  06 

— 

1-05 

— 

— 

0-40 

trace 

0-09 

— 

o-io 

trace 

trace 

— 

"  Landore  "  cylinders 

97-48 

1-05 

006 

— 

0-79 

— 

— 

— 

trace 

trace 

— 

0-38 

0-22 

trace 

— 

Unknown  origin  |  *: 

95-17 
92-58 

1-71 
0-94 

1  13 

377 

0-91 
1-49 

io-58 
0-31 

0-04 

trace 

trace 



trace 
trace 

0-22 

0-18 



0-16 
0-39 

0-03 
0-14 

trace 
trace 

0-05 

French  coinage  l    . 

97'75  i'587 

O  IO2 

— 

0-259 

— 

— 

— 

0*039 

— 

— 

0-254 

— 

— 

— 

Electrolytic  nickel 

99*22 

o'7t 

001 

0*046 

—~ 

—  —  • 

0*006 

— 

— 

— 

— 

— 

— 

— 

— 

GERMAN    SILVER 
(Argentan,  Packfong,  Alfenide) 

Owing  to  their  colour  and  stability,  these  alloys  are  used  for  domestic 
articles,  for  ornaments  in  place  of  silver,  for  coinage,  etc.  They  all  consist 
essentially  of  copper,  nickel  and  zinc,  sometimes  with  small  quantities  of 
lead  and  iron  and,  in  rare  cases,  tin  and  manganese.  Other  alloys  of  similar 
appearance,  used  for  coating  rifle  bullets  or  for  coinage,  consist  of  70-80% 
Cu,  20-30%  Ni,  and  small  proportions  of  lead,  iron,  zinc,  etc. 

The  analysis  of  german  silver  and  of  copper-nickel  alloys  in  general  is 
carried  out  as  follows : 

A.  Electrolytically  2 

In  a  small  covered  beaker,  0-5  gram  of  the  alloy  is  gently  heated  on  a 
water-bath  with  15  c.c.  of  nitric  acid  (D  1-2),  the  solution  being  subsequently 
diluted  with  20-30  c.c.  of  water.  Turbidity  indicates  tin,  which  is  deter- 
mined as  in  i  ;  a  perfectly  clear  liquid  is,  however,  used  at  once  for  the 
determination  of  copper  and  lead  (see  2). 

1.  Determination  of  the  Tin. — The  liquid  is  evaporated  to  dryness, 
the  residue  taken  up  in  a  little  water  and  a  few  drops  of  nitric  acid  and  the 
liquid  heated  for  some  time  and  filtered  through  a  compact  filter-paper 
into  a  300  c.c.  beaker.  The  precipitate  is  washed  first  with  hot  water 
slightly  acidified  with  nitric  acid  and  then  with  water  alone,  dried,  ignited 
in  a  porcelain  crucible  and  weighed  :  Sn02  x  07881  =  Sn. 

1  The  nickel  supplied  to  the  Italian  mint  for  0-2  lira  pieces  must  contain  97-50% 
Ni  and  not  more  than  1-5%  Co,  0-8%  Fe  or  0-5%  of  other  impurities. 

2  Belasio  :    Annali  Soc.  Chim.  di  Milano,   1908,  XIV,  p.  244. 


GERMAN  SILVER  269 

2.  Determination  of  the  Copper  and  Lead. — In  absence  of  tin,  the 
nitric  acid  solution  is  at  once  diluted  to  about  150  c.c.  and  electrolysed  for 
the  simultaneous  determination  of  the  copper  and  lead  (see  Electrolytic 
Determination  of  the  Copper  and  Lead  in  Ordinary  Brasses,  p.  224). 

If,  however,  the  alloy  contains  tin  and  the  solution  is  evaporated  to 
dryness  to  separate  the  metastannic  acid,  the  filtrate  is  treated  with  15  c.c. 
of  nitric  acid  (D  1*2),  diluted  to  150  c.c.  and  electrolysed. 

3.  Determination  of  the  Iron. — The  liquid  from  which  the  copper 
and  lead  have  been  separated,  together  with  the  wash  water  from  the  first 
beaker,  is  evaporated  until  white  fumes  of  sulphuric  acid  appear,  in  order 
to  transform  the  nickel  and  zinc  nitrates  into  sulphates  ;  the  10%  sulphuric 
acid  (20  c.c.)  added  to  the  electrolyte  is  sufficient  for  this  purpose.     When 
cold,  the  residue  is  taken  up  with  water  acidified  with  sulphuric  acid  and 
heated  on  the  water-bath,  the  clear  solution  being  treated  with  a  few  drops 
of  hydrogen  peroxide  and  made  alkaline  with  ammonia.     After  a  short 
rest  on  the  water-bath,  the  precipitate  is  filtered  off,  dried,  ignited  and 
weighed  :    FezO3  X  0-6994  —  Fe. 

4.  Determination  of  the  Nickel. — The  filtrate  from  the  ferric  hy- 
droxide is  made  up  to  about  150  c.c.  and  then  mixed  with  30  c.c.  of  con- 
centrated ammonia  and  o-i  gram  of  hydroxylamine  sulphate,  the  electrodes 
being  arranged  but  the  circuit  not  closed.     A  thermometer  is  fitted  and 
the  beaker  covered  with  the  two  halves  of  a  clock-glass  having  gaps  for 
the  stems  of  the  electrodes  and  for  the  thermometer  and  heated  to  90°. 
One  or  two  drops  of  fresh  concentrated  sodium  sulphite  solution  are  then 
added  and  the  electrolysis  immediately  started,  the  temperature  being  kept 
at  about  90°  and  occasional  small  quantities  of  ammonia  (i  vol.  cone, 
ammonia  to  i  vol.  water)  added  from  a  wash-bottle  to  replace  that  lost 
owing  to  the  heating  :    Winkler  cathode  ;   spiral  Winkler  anode,  ND100  = 
o-i  ampere  ;    voltage  =  2  ;    temperature  =  90°  ;    duration  (o-i  gram  Ni) 
about  2  hours. 

When  the  liquid  changes  from  blue  to  colourless,  a  drop  of  it  is  with- 
drawn and  treated  with  alcoholic  dimethylglyoxime  solution  to  ascertain 
if  the  nickel  is  completely  deposited.  When  this  is  the  case,  the  flame  is 
extinguished,  the  thermometer  taken  out  and  washed,  the  cover  removed 
and  the  electrolytic  beaker  replaced  by  another  filled  with  distilled  water. 
After  some  time  the  cathode  is  detached,  washed  with  water,  alcohol  and 
ether,  dried  at  70°  and  weighed.1 

5.  Determination  of  the  Zinc. — In  the  liquid  from  which  the  nickel 
has  been  removed,  mixed  with  the  wash  water  contained  in  the  beaker 
and  concentrated  to  about  150  c.c.,  the  zinc  is  determined  by  one  of  the 
methods  indicated  for  the  electrolytic  determination  of  zinc  in  ordinary 
brasses  (see  p.  224). 

B.  Gr a vi  metrically 

1.  Determination  of  the  Tin,  Lead,  Copper  and  Iron. — See  Gravi- 
metric Analysis  of  Ordinary  Brasses. 

1  Under  these  conditions  the  nickel  and  any  cobalt  present  are  deposited  simul- 
taneously. For  their  separation,  see  Analysis  of  Commercial  Nickel. 


270 


GERMAN  SILVER 


2.  Determination  of  the  Nickel.— The  slightly  ammoniacal  liquid 
from  which  the  ferric  hydroxide  has  been  separated  is  treated  with  slight 
excess  (about  50  c.c.  of  reagent  are  required  per  o-r  gram  nickel)  of  i% 
alcoholic  solution  of  dimethylglyoxime.     The  solution  is  heated  for  about 
30  minutes  on  the  water-bath  and — after  the  completion  of  the  precipitation 
has  been  ascertained  by  pouring  a  fresh  quantity  of  the  reagent  down  the 
sides  of  the  beaker — filtered  through  a  tared  Gooch  crucible,  which  is  re- 
peatedly washed  with  hot  water,  dried  at  120°  and  weighed :    (weight  of 
the  nickeloxime)  X  0-2032  =  nickel. 

3.  Determination  of  the  Zinc. — The  nitrate  from  the  nickel  precipitate 
is  evaporated  on  a  water-bath  with  nitric  and  sulphuric  acids  to  eliminate 
the  excess  of  alcohol  and  destroy  the  excess  of  dimethylglyoxime.     The 
residue  is  taken  up  in  water,  the  solution  neutralised  exactly  with  ammonia 
and  treated  with  8-10  drops  of  2N-hydrochloric  acid,  and  the  zinc  pre- 
cipitated as  in  the  gravimetric  analysis  of  ordinary  brasses. 

4.  Determination  of  the  Cobalt. — The  liquid  freed  from  zinc  sulphide 
is  evaporated  to  50-60  c.c.,  neutralised  with  ammonia  and  treated  at  40-50° 
with  a  current  of  hydrogen  sulphide.     The  cobalt  is  precipitated  as  sulphide, 
which  is  converted  into  sulphate  and  the  latter  weighed. 

Some  types  of  argentan  contain  also  silver  (3-10%  or  even  more).  In  this 
case,  the  silver  is  precipitated  as  chloride  before  the  copper  is  determined  (see 
Determination  of  Silver  in  Commercial  Copper).  The  nitrate  from  the  silver 
chloride  is  evaporated  in  presence  of  nitric  acid  to  expel  excess  of  hydrochloric 
acid,  the  residue  being  dissolved  in  water  and  treated  subsequently  as  above. 

Further,  manganese  is  sometimes  present.  In  this  case,  the  tin,  lead  and 
copper  are  determined  by  the  methods  given  for  complex  brasses.  The  iron 
and  manganese  are  then  precipitated  with  hydrogen  peroxide  and  ammonia, 
the  nitrate  being  employed  for  the  determination  of  the  nickel  and  zinc  as 
already  described.  The  iron  and  manganese  precipitated  with  hydrogen  peroxide 
and  ammonia  may  be  separated  and  determined  electrolytically  or  volumetrically 
(see  Complex  Brasses)  ;  or  the  ferric  and  manganese  oxides  may  be  weighed 
together,  then  dissolved  in  hydrochloric  acid,  and  the  iron  separated  as  basic 
acetate. 


As  is  seen  from  the  following  table  (Lunge),  alloys  of  copper,  nickel  and  zinc 
vary  in  composition  according  to  their  origin,  purpose,  etc. 

TABLE    XXXV 
Compositions  of  Argentans 


Cu 

Ni+Co 

Zn 

Mn 

Fe 

Pb 

Argentan  from  Krupps^  „ 

58-02 
60  -oi 

24-91 
22-69 

16-68 
16-62 

.     — 

0-25 
0-48 

O-II 

0-16 

(I    .... 

61-60 

17-00 

20-94 

0-18 

o-io 

O-2O 

,.,    JII  .      .      .      . 
Argentan  of  quality^ 

6578 
62-09 

n-43 

7'47 

22-19 
29-61 

.  

0-26 
0-25 

0-24 
o-53 

uv     ... 

70-94 

4'99 

23-63 

"~  "  ' 

0-21 

0-24 

Qualities  II,  III  and  IV  are  used  especially  for  sham  silver  ware. 


ALUMINIUM  AND   ITS  ALLOYS  271 

IMITATION    PLATE 

Imitation  plate  for  table  ware,  trays,  etc.,  consists  of  argentan  with  a 
low  proportion  of  nickel  (7-10%)  heavily  silvered  galvanically  (it  contains 
2-3%  Ag).  Besides  the  trade-mark,  it  often  exhibits — particularly  with 
forks,  spoons,  etc. — a  number  indicating  the  quantity  of  silver  deposited 
per  dozen  pieces.  The  alloy  is  analysed  like  argentan.  Usually,  however, 
it  suffices  to  determine  only  the  layer  of  silver  and  this  may  be  effected  as 
follows  : 

Determination  of  the  Silver.— i.  After  being  well  cleaned  and  freed 
from  grease,  the  object  is  suspended  by  a  platinum  wire  in  a  2-3%  potassium 
cyanide  solution  in  a  tall,  narrow  cylinder  and  is  connected  with  the  positive 
pole  of  a  current  source.  A  thin,  clean  copper  sheet  in  communication 
with  the  negative  pole,  is  also  suspended  in  the  liquid  but  not  in  contact 
with  the  object.  The  current  (o-i-0'2  ampere)  dissolves  the  silver  from 
the  article  and  deposits  it  on  the  copper.  When  the  de-silvering  is  com- 
plete, both  the  object  and  the  silvered  copper  are  removed  and  washed, 
the  latter  being  dissolved  in  nitric  acid,  the  solution  diluted  and  the  silver 
precipitated  by  a  slight  excess  of  hydrochloric  acid  ;  the  silver  chloride  is 
collected  in  a  Gooch  crucible,  washed,  dried  and  weighed. 

The  hydrocyanic  solution  is  acidified  with  dilute  hydrochloric  acid 
(under  a  hood],  the  liquid  evaporated  until  cyanogen  compounds  are  com- 
pletely eliminated,  and  the  precipitated  silver  chloride  weighed.  From 
the  sum  of  the  two  quantities  of  silver  chloride  the  amount  of  silver  on  the 
object  is  calculated. 

2.  The  article,  or  part  of  it,  is  freed  from  grease,  weighed,  and  gently 
heated  with  a  mixture  of  9  vols.  of  cone,  sulphuric  acid  and  I  vol.  of  cone, 
nitric  acid.  By  this  means  all  the  surface  silver  is  rapidly  dissolved,  whilst 
the  metal  beneath  is  not  at  all  or  but  little  attacked.  When  the  de-silvering 
is  complete,  the  object  is  withdrawn,  washed  rapidly  and  thoroughly  with 
water,1  dried  and  weighed.  The  loss  in  weight  gives  the  silver  plating. 

For  a  more  rigorous  determination  the  silver  dissolved  may  be  esti- 
mated by  diluting  with  water  the  nitric-sulphuric  solution,  together  with 
the  washing  water,  and  determining  the  silver  either  volumetrically  by 
Volhard's  method  or  gravimetrically  as  chloride. 


ALUMINIUM  AND  ITS  ALLOYS 

Owing  to  its  lightness  and  stability,  aluminium  is  now  used  for  making 
many  diverse  objects  in  common  use  and  for  naval  and  flying  construction. 
Further,  aluminium  forms  a  constituent  of  numerous  alloys,  many  of  which 
are  mechanically  superior  to  pure  aluminium.  Among  these  are  :  Light 
aluminium-bronze  (Al  with  3-8%  Cu)  ;  Magnalium  (Al  with  3-15%  Mg)  ; 
Barbouze's  alloy  (Al  with  10%  Sn)  ;  Ziskon  (Al  with  varying  proportions 
of  zinc)  ;  aluminium-nickel  (Al  with  1-3%  Ni)  ;  aluminium-manganese 

1  Thorough  washing  is  effected  by  taking  the  object  quickly  from  the  acid  mixture 
and  immersing  it  in  a  fairly  large  vessel  full  of  water. 


272  ALUMINIUM 

(Al  with  2-3%  Mn)  ;  Duralumin  (Al  with  3-5-5-5%  Cu,  0-5-0-8%  Mn, 
0-5%  Mg)  ;  Zisium  (Al  with  varying  quantities  of  Cu,  Sn,  Zn)  ;  Alluman 
(Al  with  10-20%  Sn,  4-6%  Cu).  There  are  also  many  other  alloys  of 
aluminium,  nickel  and  iron  ;  aluminium,  copper,  lead,  nickel  and  iron,  etc. 

For  commercial  aluminium  and  its  more  important  light  alloys,  a  general 
method  of  analysis  will  be  indicated,  whilst  for  light  aluminium-bronze  and 
for  magnalium,  which  could  also  be  analysed  by  the  general  method,  special 
and  quicker  methods  are  given. 

For  aluminium-copper  alloys  in  which  the  copper  predominates  (heavy 
aluminium-bronzes,  aluminium-brasses,  etc.),  reference  should  be  made 
to  copper  and  its  alloys  and  for  iron-aluminium  alloys  (ferro-aluminium) 
to  ferro-metallic  alloys. 

ALUMINIUM 

The  elements  usually  present  as  impurities  in  commercial  aluminium 
are  copper,  lead,  iron,  zinc,  carbon,  silicon  and  sodium.  To  form  the  so- 
called  light  alloys,  the  aluminium  may  be  associated  with  tin,  copper,  zinc, 
nickel,  cobalt,  manganese,  lead,  magnesium,  etc. 

Thus,  the  analysis  of  commercial  aluminium  or  of  its  lighter  alloys 
includes  J  : 

1.  Determination  of  the  Copper,  Lead,  Iron,  Zinc,  Manganese 
and  Cobalt. — A .  IN  ABSENCE  OF  NICKEL.  From  2  to  4  grams  of  the  sample 
— according  as  the  extraneous  metals  are  present  in  larger  or  smaller  pro- 
portion— in  minute  fragments  are  treated  in  a  flask  (about  ^-litre)  with 
five  times  their  weight  of  tartaric  acid  and  a  little  water.  The  flask  is 
covered  with  a  small  funnel  and  a  small  quantity  of  hydrochloric  acid 
diluted  with  an  equal  volume  of  water  added  drop  by  drop.  The  action  is 
started  by  gentle  heating  and  sometimes  proceeds  so  vigorously  as  to  require 
cooling.  When  the  evolution  of  hydrogen  begins  to  slacken,  a  fresh  quantity 
of  hydrochloric  acid  of  the  same  concentration  is  added  and  the  liquid 
heated  on  the  water-bath  until  the  action  is  complete,  care  being  taken  to 
use  the  least  possible  amount  of  acid.  The  heating  is  then  continued  for 
some  time,  with  addition  of  2-3  c.c.  of  cone,  nitric  acid. 

The  solution,  which  is  usually  turbid  owing  to  the  presence  of  carbon 
and  silica,  is  treated  with  small  quantities  of  50%  sodium  hydroxide  solution 
until  the  voluminous  aluminium  hydroxide  precipitate  at  first  formed 
redissolves  in  the  excess  of  the  reagent.  Hydrogen  sulphide  is  then  passed 
through  until  the  supernatant  liquid  becomes  faintly  yellow  and  the  solution 
boiled  for  some  minutes  to  facilitate  separation  of  the  sulphides,  left  for 
a  time  on  the  water-bath  and  filtered  into  a  300  or  500  c.c.  measuring  flask, 
the  precipitate  being  washed  with  hot  water  containing  a  few  drops  of 
sodium  sulphide.  The  copper,  lead,  iron,  zinc,  manganese  and  cobalt 
remain  on  the  filter,  while  the  aluminium  passes  into  solution,  together 
with  any  tin  present  as  sulphostannate. 

The  sulphides  on  the  filter  are  dissolved  in  nitric  acid  (D  1-2)  and  the 

1  Belasio  :  Annali  di  Chim.  Appl.,  1914,  I,  p.  101  ;  Ann.  Labor.  Chim,  Gabelle, 
VII,  p.  171. 


ALUMINIUM  273 

metals  determined  as  in  the  case  of  ordinary  brasses  when  manganese  is 
absent,  or  like  complex  brasses  when  manganese  is  present.1 

B.  IN  PRESENCE  OF  NICKEL.  In  this  case,  the  preliminary  removal  of 
the  nickel  as  nickeloxime  is  necessary.  When  the  metal  is  attacked  as 
described  above,  the  liquid  is  filtered  to  remove  the  suspended  carbon  and 
silica,  these  being  washed  and  the  filtrate  treated  with  ammonia  until  the 
copious  precipitate  first  forming  redissolves.  The  last  clots  of  precipitate 
are  dissolved  by  heating  on  a  water-bath  and  the  clear  liquid  treated  with 
i%  alcoholic  dimethylglyoxime  solution  in  slight  excess.  After  a  short 
stand  on  a  water-bath  the  precipitate  is  collected  in  a  Gooch  crucible,  washed 
firstly  with  hot  water  containing  a  little  ammonia  and  ammonium  tartrate 
and  then  with  hot  water  alone  until  the  filtrate  is  neutral,  dried  at  120° 
and  weighed  :  nickeloxime  X  0-2032  =  nickel. 

The  filtrate  is  heated  on  a  water-bath  to  expel  the  alcohol  and  then 
treated  with  just  sufficient  hydrogen  sulphide  to  precipitate  the  metals  in 
solution,  the  subsequent  procedure  being  as  in  A  (above). 

2.  Determination  of  the  Tin. — The  sodium  or  ammonium  sulphide 
solution  in  the  300  or  500  c.c.  flask  is  made  up  to  volume  and  an  aliquot 
part  (100  or  150  c.c.)  treated,  in  a  J-litre  flask  covered  with  a  small  funnel, 
with  small  quantities  of  hydrochloric  acid  and  with  shaking  until  the  re- 
action is  acid.     A  further  quantity  of  25-30  c.c.  of  cone,  hydrochloric  acid 
is  added  and  the  liquid  boiled,  if  necessary  with  addition  of  a  few  crystals 
of  potassium  chlorate,  until  the  tin  sulphide  at  first  separating  redissolves 
in  the  excess  of  hydrochloric  acid. 

The  solution  is  then  treated  with  25-30  grams  of  ammonium  oxalate 
and  electrolysed  at  50-60°  to  determine  the  tin  (see  Electrolytic  Determina- 
tion of  Tin  in  Ordinary  Bronzes).  > 

3.  Determination  of  the  Carbon. — This  is  carried  out  directly  on  a 
portion  of  the  sample  by  either  the  Corleis  method  or  the  copper  chloride 
method  (see  Determination  of  Total  Carbon  in  Iron). 

4.  Determination  of  the  Silicon.2 — i   gram   of   the   aluminium    in 
small  fragments  is  dissolved  in  300  c.c.  of  a  mixture  of  100  c.c.  of  nitric 
acid  (D  1-42),  300  c.c.  of  hydrochloric  acid  (D  1-2)  and  600  c.c.  of  25% 
sulphuric  acid.     When  the  action  comes  to  an  end,  the  liquid  is  heated 
carefully  on  a  sand-bath  until  abundant  white  sulphuric  acid  fumes  appear. 
When  cold  the  residue  is  taken  up  with  water  acidified  with  sulphuric  acid, 
heated  to  dissolve  the  aluminium  sulphate  and  filtered,  the  vessel  and  filter 
being  washed  first  with  water  acidified  with  sulphuric  acid  and  then  with 
water  alone.3    The  residue  on  the  filter,  consisting  of  silica,  graphitic  silicon 
and  a  little  alumina,  is  dried,  ignited  and  fused  with  sodium  carbonate,  the 
cold  mass  being  dissolved  in  water  acidified  with  hydrochloric  acid  and 
evaporated  to  dryness  ;   this  treatment  with  hydrochloric  acid  is  repeated 
several  times  and  the  residue  finally  heated  in  an  oven  at  135°  to  render 
the  silica  completely  insoluble  (see  Iron,  2). 

1  Any  cobalt  present  is  determined  electrolytically  under  the  conditions  indicated 
for  the  determination  of  the  nickel. 

2  According  to  I.  O.  Handy:  Journ.  Amer.  Chem.  Soc.,  XVIII,  p.  736. 

3  In  presence  of  lead,  the  washing  is  carried  out  first  with  hydrochloric  acid  (D  1-2) 
and  then  with  water,  as  usual. 

A.C.  18 


274  ALUMINIUM 

The  silica,  often  contaminated  with  alumina,  is  filtered  off,  dried,  ignited 
in  a  platinum  crucible  and  weighed  ;  it  is  then  evaporated  on  a  water- 
bath  with  a  few  drops  of  sulphuric  acid  and  a  few  c.c.  of  hydrofluoric  acid, 
heated  to  redness  and  weighed.  The  loss  in  weight  gives  the  silica  :  Si02  X 
0-4693  =  Si. 

5.  Determination  of  the  Sulphur,  Arsenic  and   Phosphorus.— *io 
grams  of  the  sample  are  introduced  into  a  flask  fitted  with  a  tapped  funnel 
and  a  gas-delivery  tube  connected  with  absorption  bulbs  containing  bromine 
water,  and  very  dilute  hydrochloric  acid  slowly  run  in  through  the  funnel 
until  the  metal  is  completely  attacked.     The  sulphur,   phosphorus  and 
arsenic  are  oxidised  by  and  retained  by  the  bromine  water,  one-half  of  which 
is  used  for  the  determination  of  the  sulphuric  acid  by  precipitation  with 
barium  chloride.     The  second  half  is  freed  from  the  excess  of  bromine 
and  the  arsenic  precipitated  by  means  of  hydrogen  sulphide  and  deter- 
mined as  usual.     The  filtrate  from  the  arsenic  precipitate  is  freed  from 
excess  of  hydrogen  sulphide  and  the  phosphoric  acid  then  precipitated 
with  ammonium   molybdate  (see   Determination    of   the    Phosphorus   in 
Iron). 

6.  Determination    of    the    Sodium.1 — 5  grams    of   the   sample  are 
heated  gently  with  nitric  acid  (D  1-15),  the  solution  evaporated  in  a  porcelain 
dish,  the  residue  dried  and  heated  for  a  long  time  on  a  sand-bath,  but  without 
melting  the  sodium  nitrate  formed.     When  cold  the  residue  is  taken  up  in 
boiling  water,  the  solution  filtered  and  the  filter  washed  with  boiling  water, 
the  filtrate  being  evaporated  to  dryness  repeatedly  with  hydrochloric  acid 
to  expel  the  nitric  acid  and  the  residue  heated  to  about  300°,  allowed  to 
cool,  dissolved  in  water  and  the  chlorine  estimated  ;    the  corresponding 
amount  of  sodium  is  then  calculated. 

Lunge  2  observes  that  a  little  sodium  aluminate  is  formed  under  these 
conditions  and  advises  the  treatment  of  the  aqueous  solution  with  ammo- 
nium carbonate  to  precipitate  the  aluminium  and  the  determination  of 
the  sodium  as  sulphate  in  the  filtrate. 

7.  Determination   of  the   Aluminium. — 0-6  gram   of   the   sample, 
reduced  to  fine  fragments,  is  treated  in  a  flask  covered  with  a  small  funnel, 
with  hydrochloric  acid  diluted  with  an  equal  volume  of  water.     When 
the  action  is  complete,  the  solution  is  evaporated  in  a  platinum  dish  on  a 
water-bath,  this  evaporation  with  dilute  hydrochloric  acid  being  repeated 
several  times  and  the  residue  finally  heated  in  an  oven  at  135°  to  render 
the  silica  insoluble.     The  latter  is  treated  with  hot  water  acidified  with 
hydrochloric  acid  and  filtered  into  a  250  c.c.  beaker,  in  which  it  is  subjected 
to  a  current  of  hydrogen  sulphide.     The  precipitate  is  filtered  off  and  both 
vessel  and  filter  washed  with  hot  water  containing  hydrogen  sulphide,  the 
filtrate  being  collected  in  a  300  c.c.  flask,  boiled  to  expel  hydrogen  sulphide, 
treated  with  a  few  drops  of  cone,  nitric  acid,  heated  again  to  oxidise  the 
iron,   cooled   and   made  up   to   volume.     100  c.c.    of   the  liquid  (=  0-2 
gram  of  metal)  are  treated  in  a  platinum  dish  or,  failing  that,  a  porcelain 
one,  with  excess  of  ammonium  chloride  and  sufficient  ammonia  to  give  a 

1  Moissan  :    Comptes  rendus,   1895. 

2  Lunge  :  Technical  Methods  of  Chemical  Analysis  (London,  1911),  Vol.  II,  p.  348. 


ALUMINIUM  275 

faintly  alkaline  reaction.  The  liquid  is  boiled  for  some  time  and  the  alu- 
minium and  ferric  hydroxides  filtered  off,  washed,  dried  and  weighed  in 
the  ordinary  manner.  This  amount,  less  that  of  the  ferric  oxide  previously 
found,  gives  the  alumina  and  hence  the  aluminium. 

If  the  iron  has  not  been  determined  previously,  it  may  be  estimated 
in  presence  of  aluminium  by  means  of  cupferron. 

For  this  purpose,  100  c.c.  of  the  liquid  in  the  flask  are  treated  in  a  250 
c.c.  beaker,  with  constant  shaking,  with  6%  aqueous  cupferron  (ammonium 
salt  of  nitrosophenylhydroxylamine)  until  the  precipitation  of  the  iron  is 
complete  (o-i  gram  Fe  requires  0-833  gram  of  the  reagent).  The  end  of  the 
reaction  is  detected  by  pouring  a  little  of  the  reagent  down  the  side  of  the 
beaker ;  when  iron  is  still  present,  a  reddish-brown  precipitate  is  formed 
whereas  in  absence  of  iron  a  white,  crystalline  precipitate  is  formed  owing 
to  the  slight  solubility  of  the  reagent  in  an  acid  medium. 

After  the  precipitation  of  the  iron,  the  liquid  is  left  for  15-20  minutes 
and  then  filtered,  the  precipitate  being  thoroughly  washed  first  with  2N 
hydrochloric  acid,  then  with  slightly  ammoniacal  water  to  eliminate  all 
traces  of  the  reagent,  and  finally  with  distilled  water.  The  moist  filter 
and  precipitate  are  then  carefully  ignited  in  a  porcelain  crucible,  the  weight 
giving  the  ferric  oxide.1 

8.  Determination  of  the  Nitrogen. — From  3  to  4  grams  of  the  sample 
are  dissolved,  in  a  flask  fitted  with  a  tapped  funnel  and  a  gas  delivery  tube, 
with  10%  sodium  hydroxide  solution,  the  gas  generated  being  collected  in 
dilute  hydrochloric  acid.  At  the  end  of  the  action,  the  flask  is  boiled  for 
a  further  15  minutes  to  displace  all  the  ammonia  and  the  nitrogen  in  the 
hydrochloric  acid  then  determined  colorimetrically  with  Nessler  solution, 
comparison  being  made  with  a  standard  ammonium  chloride  solution. 


*** 


Aluminium  of  good  quality  should  be  white  with  only  a  faint  blue  tint  and 
should  be  highly  ductile  and  malleable,  while  its  fracture  should  be  finely  crys- 
talline, uniform,  and  free  from  sponginess  or  slag.  Its  specific  gravity  should  be 
between  2-6  and  2-7  (the  value  increases  with  the  degree  of  impurity)  and  the 
percentage  of  aluminium  at  least  97-98,  the  total  amount  of  elements  commonly 
accompanying  the  aluminium  (silicon,  iron,  copper)  not  exceeding  1-5-2%. 
According  to  Moissan,  a  particularly  harmful  influence  on  the  strength  and 
durability  of  the  aluminium,  especially  when  this  is  to  come  into  contact  with 
water,  is  exercised  by  sodium,  which  may  be  present  in  the  proportion  of  o-i- 
0-4%  (Moissan)  or,  according  to  some,  in  even  larger  amounts  (up  to  4%). 
According  to  Foundry,  aluminium  also  contains  0-04-0-12%  of  nitrogen.  The 
compositions  of  various  samples  are  given  in  the  following  table  (Moissan, 
Campredon,  Lunge)  : 

1  In  the  liquid  from  which  the  aluminium  and  iron  have  been  separated,  the  mag- 
nesium is  determined  in  the  usual  manner. 


276 


ALLOYS   OF  ALUMINIUM  AND  MAGNESIUM 


TABLE    XXXVI 
Compositions  of  Samples  of  Aluminium 


Source. 

Al 

Fe 

Cu 

Si 

Na 

C 

Pb 

P 

S 

Bussi         (I1 

98-86 

o-77 

0-29 

(Abruzzi)     \  II1 

98-90 

0-58 

— 

0-50 

— 

— 

— 

— 

— 

(ill1 

99-00 

0-51 

— 

0-47 

— 



— 

— 

— 

„         ("  Quality  o 

99-90 

0-04 

— 

0-06 

— 

— 

— 

— 

— 

hausenj       "       ,, 

99-33-99-6i 
92-84-97-65 

0-11-0-34 
1-37-3-34 

~ 

0-18-0-58 
0-94-3-82 

~ 

~ 

~ 

— 

z 

Pittsburg. 

98-82 

0-27 

o-35 

0-15 

o-io 

0-41 

— 

— 

— 

Samples   of    un-  ^  T 
known  origin       \,, 
(Campredon)        ) 

98-4434 
96-5501 

0-586 
1-2320 

0-479 
0-939 

0-1463 
0-1979 

0-14 

O-O2 

O-IO 

0-05 

0-073 
0-6270 

1-029 
0-005 

0-0027 
0-0038 

ALLOYS    OF    ALUMINIUM    AND    COPPER2 
(Light  Aluminium -bronzes) 

Light  aluminium-bronzes  have  the  specific  gravity  about  3  and  exhibit 
mechanical  properties  superior  to  those  of  pure  aluminium,  so  that  they 
are  used  in  the  construction  of  parts  for  automobiles,  dirigible  balloons, 
aeroplanes,  etc.  ;  those  most  commonly  used  contain  3-8%  of  copper. 
In  practice  the  most  important  determination  is  that  of  the  copper. 

1.  Determination  of  the  Copper. — i  gram  of  the  alloy  as  filings 
is  acted  on  in  a  platinum  dish  with  5  grams  of  sodium  hydroxide  dissolved 
in  25  c.c.  of  water.  When  the  action  is  complete,  the  insoluble  residue, 
consisting  of  copper,  iron,  etc.,  is  collected  on  a  filter,  washed  well,  dissolved 
in  10-15  c.c.  of  nitric  acid  (D  1-2)  and  the  solution,  after  suitable  dilution, 
electrolysed  to  determine  the  copper  (see  Electrolytic  Determination  of 
Copper  in  Ordinary  Brasses). 


ALLOYS    OF    ALUMINIUM    AND    MAGNESIUM 

(Magnalium) 

The  most  important  determination  with  these  alloys  is  that  of  the 
magnesium.  I  gram  of  the  alloy  is  treated  with  a  mixture  of  hydro- 
chloric, nitric  and  sulphuric  acids,  the  liquid  being  heated  until  white  fumes 
appear  and  the  silica  removed  by  filtration  (see  Determination  of  Silicon 
in  Aluminium).  In  the  filtrate  the  copper,  lead,  etc.,  are  precipitated  with 
hydrogen  sulphide,  the  precipitate  being  filtered  off,  the  excess  of  hydrogen 
sulphide  eliminated,  the  iron  oxidised  and  the  solution  neutralised  with 
ammonia,  diluted  considerably  and  treated  with  30  c.c.  of  concentrated 
ammonium  acetate  solution.  The  liquid  is  then  boiled  to  precipitate  the 

1  Kindly  communicated  privately. 

2  For  alloys  of  aluminium  and  copper  (aluminium  bronzes)  with  a  preponderance 
of  copper,  see  Special  Bronzes. 


SILVER  ALLOYS  277 

aluminium  and  filtered,  the  filtrate  being  used  for  the  determination  of  the 
magnesium  in  the  ordinary  way. 

Magnalium  usually  contains  2%  of  magnesium  but  may  contain  up  to  15%. 
It  is  lighter,  harder  and  more  easily  worked  than  aluminium. 


SILVER  AND  ITS  ALLOYS 

The  most  important  of  these  products  are  silver  in  rods,  ingots,  bar, 
etc.,  and  its  alloys  with  copper.  Their  analysis  involves  in  all  cases  the 
same  procedure. 

SILVER 

See  following  article  for  the  determinations  to  be  made. 


SILVER   ALLOYS 

In  commercial  silver  and  its  alloys  with  copper,  the  most  important 
determination  is  that  of  the  silver,  since  these  products  are  valued  according 
to  their  silver  content,  referred  to  1000  parts.  In  some  cases  determination 
of  the  small  quantity  of  gold  present  may  be  of  interest,  and  in  some  instances 
also  that  of  the  bismuth.  In  alloys  of  silver  with  gold  or  with  gold  and 
copper,  it  is  usual  to  determine  both  the  rare  metals  (see  Gold  and  its  Alloys). 
In  all  cases  the  sampling  is  of  great  importance. 

Sampling.  Silver  alloys,  especially  those  with  copper,  are  mostly  non- 
homogeneous,  since  their  solidification  is  accompanied  by  the  phenomenon 
of  liquation.  With  silver-copper  alloys  less  than  718  fine  (718/1000)  the  outer 
parts  are  richer  than  the  central  ones,  whereas  with  those  more  than  718 
fine  the  reverse  is  the  case.  It  is,  therefore,  difficult  to  obtain  a  represen- 
tative sample.  The  most  accurate  method  is  to  take  the  sample  from  the 
fused  metal  in  the  following  way  :  The  liquid  mass  is  stirred  by  means 
of  a  graphited  iron  spoon,  which,  when  thoroughly  heated,  is  extracted  full 
of  metal,  two  drops  of  the  latter,  weighing  about  3-4  grams  each,  being 
dropped  into  a  cast-iron  mould.  These  drops  are  then  flattened  on  an 
anvil,  rolled  to  obtain  sheet  that  can  easily  be  cut  with  metal  shears,  and 
polished  with  emery  cloth. 

With  ingots,  where  this  method  is  impracticable,  four  samples  are  taken 
with  a  drill  at  different  points,  namely :  two  outside  on  the  vertices  of  a 
diagonal  of  the  cake  of  metal  and  two  on  two  points  of  the  diagonal  itself 
at  distances  of  one-fourth  and  three-fourths  of  the  length  of  the  diagonal 
from  one  of  the  vertices,  the  two  holes  being  made  one  at  the  top  and  the 
other  at  the  bottom  of  the  ingot  and  the  first  borings  discarded  so  as  to 
collect  portions  lying  approximately  on  the  diagonal. 

With  finished  products,  jewellery,  gilt  ware,  etc.,  the  surface  must  be 
filed  away,  since  they  are  generally  whitened  and  the  outer  parts  may  be 
richer  in  silver. 


278  SILVER  ALLOYS 

In  whatever  way  the  sample  is  taken,  the  determinations  should  always 
be  executed  in  duplicate. 

1.  Determination  of  the  Silver. — The  methods  most  commonly  used 
are  :    the  dry  or  cupellation  method,  Volhard's  volumetric  method  with 
thiocyanate,  and  Gay-Lussac's  sodium  chloride  method. 

(a)  CUPELLATION  METHOD.  This  method  is  based  on  the  fact  that  the 
noble  metals,  silver,  gold  and  platinum,  are  unoxidisable  at  the  highest 
temperatures,  whilst  copper  and  other  metals  Usually  alloyed  to  the  precious 
metals  oxidise  easily  and,  if  in  presence  of  a  certain  quantity  of  lead — which 
gives  a  readily  fusible  oxide — penetrate  by  imbibition  into  the  cupel.  Thus, 
the  noble  metals  are  separated  in  the  form  of  a  drop,  which,  on  cooling, 
yields  a  button  capable  of  direct  weighing. 

Apparatus  and  reagents,  (i)  Muffle  furnace,  either  coal  or  gas,  the 
latter  more  easy  to  manipulate  and  regulate.  In  order  to  protect  the 
operator  from  the  intense  heat  of  the  furnace,  the  latter  is  usually  placed 
in  an  adjacent  room  close  to  the  dividing  wall,  a  small  aperture  in  which 
gives  access  to  the  orifice  of  the  muffle. 

2.  Cupels.     These  are  capsules  having  the  form  of  an  inverted,  trun- 
cated cone  and  made  with  bone  dust  carefully  powdered,  calcined,  washed 
and  pressed  in  a  mould.     A  good  cupel  should  absorb  its  own  weight  of 
lead. 

3.  A  thermo-electric  couple  with  the  corresponding  pyrometer  volt- 
meter, to  measure  the  temperature  of  the  muffle.     The  couple  is  placed 
in  the  muffle  so  that  its  extremity  is  very  close  to  the  cupel. 

4.  Lead  free  from  silver.     That  obtained   by  reducing  litharge  could 
be  used  but  its  price  is  too  high.     Lead  almost  entirely  free  from  silver  is, 
however,  sold  and  is  quite  suitable  ;  20  grams  of  it  should  be  cupelled  as  a 
check. 

Preliminary  test.  The  amount  of  lead  to  be  used  for  the  cupellation 
varies  with  the  silver  content  of  the  sample,  so  that  it  is  necessary  to  make 
a  preliminary  test.  The  external  characters  and  a  test  on  the  touchstone 
are  sufficient  to  a  skilled  operator.  A  beginner  may  make  use  of  a  method 
which  is  sometimes  employed  and  which  consists  in  cupelling  o-i  gram  of 
the  sample  with  0-5  gram  of  lead  if  the  metal  is  soft  and  white,  with  I  gram 
of  lead  if  it  is  hard,  or  with  1-5  gram,  if  it  appears  reddish. 

The  amounts  of  lead  to  be  used  for  different  degrees  of  fineness  are  as 
follows  : 

Degree  of  fineness  Amount  of  lead  to  cupel 

of  the  alloy.  i  gram  of  the  sample 

1,000       .......       0-3  gram. 

95° 3'° 

900       .......        7-0       ,, 

800       .......      10-0       ,, 

70O          .......        12-0          „ 

6OO          .......        14-0          ,, 

6OO-O     .......        16-17     „ 

Actual  test.  If  the  fineness  is  above  800,  two  samples  of  i  gram  each, 
and  if  less  than  800,  two  samples  of  0-5  gram  each  are  weighed  with  the 


SILVER  ALLOYS  ,279 

greatest  accuracy.1  These  are  wrapped  in  small  pieces  of  white  paper  or 
thin  lead  foil,  the  weight  of  which  is  allowed  for  in  calculating  the  amount 
of  lead  to  be  used,  and  placed  on  a  tray  consisting  of  a  sheet  of  copper  pro- 
vided with  a  handle  and  stamped  into  cavities  to  take  the  test  pieces.  Be- 
side each  button  is  placed  the  necessary  quantity  of  lead. 

The  cupels  are  placed  in  the  muffle  and  close  to  them  the  thermo-electric 
couple,2  the  temperature  being  then  raised  to  bright  redness,  that  is,  to 
about  950°.  When  these  have  assumed  the  temperature  of  the  muffle 
(indicated  by  the  absence  of  a  dark  zone  between  the  bottom  of  the  cupel 
and  the  base  of  the  muffle),  the  pieces  of  lead  are  introduced  into  the  cupels 
by  means  of  suitable  tongs.  The  lead  at  first  melts  and  becomes  covered 
with  a  layer  of  oxide  and  after  some  time  uncovers,  that  is,  assumes  a  shiny 
appearance. 

When  the  lead  is  uncovered,  the  test  pieces  are  placed  in  the  cupels  with 
great  care  to  avoid  loss  by  projection,  the  door  of  the  muffle  being  left  open 
a  little  to  permit  of  observation  and  to  give  access  to  the  air.  The  test 
pieces  melt  and  a  shining  appearance  is  resumed.  Over  the  surface  of  the 
fused  metal,  which  is  at  first  only  slightly  convex,  luminous  points  are  seen 
to  run  and  become  absorbed  by  the  cupel.  As  the  cupellation  proceeds  the 
convexity  increases  and  the  drops  of  fused  litharge,  of  oily  appearance, 
become  larger  and  circulate  more  rapidly.  At  this  point  the  temperature 
should  be  raised  a  little  by  closing  the  door  of  the  muffle  and  increasing  the 
draught  of  the  furnace,  in  order  to  oxidise  the  last  particles  of  lead  and 
keep  the  button  of  silver  fused.  As  the  last  portions  of  lead  "  pass  "  from 
the  silver,  the  molten  metal,  which  is  in  a  state  of  considerable  agitation, 
exhibits  a  kind  of  iridescence,  this  soon  disappearing  *  the  button  then 
appears  opaque  and  still,  but  suddenly  flashes  out  brightly.  This  indicates 
the  end  of  the  operation. 

The  cupels  are  then  gradually  brought  near  to  the  door  of  the  muffle 
so  that  the  buttons  of  silver  may  cool  slowly  and  rapid  release  of  the  occluded 
oxygen  (fused  silver  absorbs  up  to  22  volumes  of  oxygen)  not  give  rise  to 
projection  (spitting  or  vegetating)  of  the  metal.  After  a  few  minutes  the 
cupels  are  withdrawn  from  the  muffle  and  the  metallic  buttons  detached, 
hammered  slightly  on  both  sides,  held  in  tongs  and  freed  with  a  scratch- 
brush  from  the  adherent  cupel  dust  and  weighed. 

The  total  weight  of  the  two  test  pieces  in  milligrams,  if  these  were  each 
of  0-5  gram,  or  this  weight  divided  by  two,  if  the  samples  were  i  gram  each, 
gives  the  fineness  of  the  alloy. 

If  the  cupellation  is  successful,  the  silver  buttons  obtained  from  the 

1  With  samples  of  silver  and  gold,  to  obtain  the  highest  accuracy  and  to  be  able 
to  weigh  directly,  very  sensitive  balances  are  employed  with  an  exactly  equally  divided 
long  beam  and  with  very  small  movable  dish-shaped  pans,  on  which  the  test  pieces 
are  placed  directly.     The  maximum  load  of  such  a  balance  is  2-3  grams. 

2  If  no  thermo-electric  couple  and  corresponding  voltmeter-pyrometer  are  available, 
the  temperature  of  the  furnace  during  cupellation  may  be  regulated  by  observation 
of  the  way  in  which  the  fumes  of  litharge  are  evolved.     When   the  temperature  is 
suitable,  the  fume  rising  from  the  tests  should  reach  only  half-way  up  the  muffle  and 
small,  lamellar  crystals  of  litharge  should  be  seen  on  the  edge  of  the  cupel.     If  the 
temperature  is  too  low,  the  fume  licks  round  the  edges  of  the  cupel,  whilst,  if  too  high, 
it  rises  rapidly  towards  the  crown  of  the  muffle. 


280  SILVER  ALLOYS 

two  tests  should  have  shining,  hemispherical  upper  surfaces  and  opaque, 
white  lower  ones,  and  should  differ  in  weight  by  a  few  milligrams  at  most. 

The  method  of  cupellation,  largely  used  for  the  analysis  of  argentiferous 
minerals  and  for  the  control  of  intermediate  products  in  the  extraction  of  silver, 
as  well  as  for  the  by-products  and  for  low-grade  alloys,  is  not  advisable  for 
analysing  ordinary  jewellery,  coinage,  etc.,  since,  however  carefully  it  is  carried 
out,  the  results  obtained  are  not  always  concordant  and  never  very  exact,  being 
mostly  somewhat  low.  The  errors  are  due  principally  to  volatilisation  of  the 
silver  and  absorption  by  the  cupel.  Tables  showing  the  corrections  to  be  applied 
have  been  prepared,  but  the  best  method  of  determining  such  corrections  is 
to  carry  out  a  check  determination,  at  the  same  time  and  under  the  same  con- 
ditions, with  pure  silver  and  pure  copper  in  approximately  the  same  proportions 
as  in  the  sample. 

As  regards  the  influence  of  extraneous  metals  on  the  results,  it  should  be 
borne  in  mind  that  gold  and  platinum  remain  with  the  silver  and  increase  its  weight. 
They  may  be  detected  by  treating  the  button  with  nitric  acid  and  examining  the 
black  powder  remaining  undissolved.  In  low  proportions,  arsenic,  tin,  antimony, 
bismuth,  iron,  nickel  and  cobalt  do  not  interfere  appreciably  with  the  operation. 

(6)  VOLHARD'S  METHOD.1  This  method  consists  in  precipitating  the 
silver  in  nitric  acid  solution  with  standard  ammonium  thiocyanate  solution 
in  presence  of  ferric  sulphate  as  indicator.  As  soon  as  the  precipitation  of 
the  silver  is  complete,  the  thiocyanate  reacts  with  the  ferric  salt  and  gives 
a  persistent  red  coloration,  which  marks  the  end  of  the  reaction. 

Reagents,  (i)  A  solution  containing  3-1-3-2  grams  of  ammonium 
thiocyanate,  free  from  chlorides,  per  litre. 

(2)  Cold  saturated  ferric  ammonium  alum  solution  free  from  chlorides, 
and  treated  with  a  little  nitric  acid  to  destroy  the  brown  colour  ;  the  same 
amount  (2-3  c.c.)  is  used  in  each  titration. 

(3)  Pure  silver  (fine  silver}.     This  may  be  obtained  in  foil  from  reputable 
firms. 

Where  many  tests  are  made  the  fine  silver  is  prepared  in  the  laboratory 
from  the  silver  chloride  residues  from  Gay-Lussac's  method  or  from  silver 
chloride  precipitated  from  the  silver  nitrate  solutions  obtained  in  the  quarta- 
tion  of  gold  (see  later).  Failing  these,  commercial  silver  of  999  fineness  is 
dissolved  in  nitric  acid,  allowed  to  stand  for  some  days  in  the  dark,  filtered 
to  remove  traces  of  undissolved  gold  and  the  silver  precipitated  with  a 
slight  excess  of  dilute  hydrochloric  acid. 

In  whatever  way  obtained,  the  silver  chloride  is  washed  free  from  acid, 
dissolved  in  ammonia,  left  for  some  days  and  then  filtered,  the  clear  solution 
being  made  acid  with  dilute  hydrochloric  acid  to  precipitate  the  silver 
chloride,  which  is  again  washed  free  from  acidity  and  redissolved  in  ammonia. 
After  standing  for  some  time,  the  solution  is  filtered,  treated  with  sodium 
hydroxide  in  the  proportion  of  750  grams  per  1000  grams  of  the  chloride 
and  heated  to  boiling,  150-200  grams  of  pure,  powdered  glucose  being  added 
in  small  amounts  and  the  liquid  kept  boiling  for  about  30  minutes.  The 
spongy  silver  thus  obtained  is  pumped  off,  thoroughly  washed,  dried  and 
fused  in  a  refractory  crucible  with  a  little  nitre  and  borax. 

When  cold,  the  crucible  is  broken  and  the  metallic  button  washed  with 
1  Also  known  as  the  Charpentier-Volhard  method. 


SILVER  ALLOYS  281 

dilute  sulphuric  acid,  dried,  re-melted  alone  in  a  smaller  crucible  and  poured 
into  a  small  ingot-mould  heated  and  greased  with  tallow  or  vaseline.  The 
ingot  obtained  is  thoroughly  cleaned,  washed  first  with  dilute  sulphuric 
acid  and  then  with  water  and  dried.  It  is  then  cut  into  pieces  with  a  chisel, 
and  these  rolled  into  strips  easily  cut  with  the  metal  shears.1 

Titration  of  the  thiocyanate  solution.  Exactly  0-2  gram  of  fine  silver  is 
heated  gently  with  5-10  c.c.  of  nitric  acid  (D  1-2)  in  a  conical  flask  covered 
with  a  funnel  until  the  metal  is  dissolved  and  the  red  fumes  have  disappeared. 
The  funnel  is  removed  after  cooling  and  washed  with  distilled  water,  the 
solution  being  treated  with  50  c.c.  of  cold  water  and  2-3  c.c.  of  the  ferric 
alum  solution,  and  the  thiocyanate  solution  gradually  run  in  from  a  burette 
until  the  milky  liquid  assumes  a  persistent  pink  tint.  It  is  usual  to  adjust 
the  strength  of  the  thiocyanate  solution  so  that  0-2  gram  of  silver  requires 
exactly  50  c.c. 

Procedure  in  the  actual  test.  Exactly  0-2  gram  of  the  sample  is  dissolved 
in  nitric  acid  z  as  described  above  and  the  solution  diluted  and  titrated 
with  the  thiocyanate. 

The  Volhard  method  is  very  rapid  and  applicable  to  alloys  of  any  degree 
of  fineness  but  is  not  so  exact  as  Gay-Lussac's  method  (c).  Further,  it  cannot 
be  used  in  presence  of  mercury  or  palladium,  since  these  metals  also  react  with 
thiocyanate.  Also,  with  more  than  70%  of  copper,  the  blue  coloration  renders 
the  end-point  less  exact ;  in  this  case  fine  silver  may  be  added  so  as  to  diminish 
the  proportion  of  copper.  Nickel  and  cobalt  have  a  similar  effect  to  copper. 

(c)  GAY-LUSSAC'S  METHOD.  This  was  proposed  in  1832,  when  the 
French  Minister  of  Finance  appointed  a  commission,  of  which  Gay-Lussac 
was  a  member  and  also  reporter,  to  study  the  causes  of  error  in  the  deter- 
mination of  silver  by  the  cupellation  method.8 

It  consists  in  adding  to  a  nitric  acid  solution  of  the  sample  sufficient 
sodium  chloride  solution  to  precipitate  almost  the  whole  of  the  silver,  and 
in  estimating  the  small  amount  of  silver  remaining  in  solution  from  the 
faint  turbidity  produced  by  addition  of  a  fresh  quantity  of  the  sodium 
chloride  solution.  With  a  little  practice,  I  part  in  10,000  may  be  deter- 
mined accurately  by  this  method.  Since  it  requires  a  knowledge  of  the 
approximate  composition  of  the  sample,  a  preliminary  test  by  Volhard's 
method  or  by  cupellation  is  necessary. 

Apparatus,  i.  Ordinary  bottles  of  about  200  c.c.  capacity,  fitted  with 
tight-fitting  ground  stoppers  and  with  a  distinctive  mark  on  both  bottle 
and  stopper. 

2.  A  100  c.c.  pipette.  The  pipettes  used  by  assayers  are  usually  without 
a  stem  and,  to  facilitate  reading,  are  fixed  in  a  stand  (Fig.  24). 

Increased  accuracy  of  measurement  is,  however,  obtained  by  means  of 
the  Stas  pipette  (Fig.  25),  which  is  a  100  c.c.  pipette  drawn  out  to  a  point 

1  This  method  for  obtaining  fine  silver  is  that  adopted  by  the  testing  laboratory 
of  the  Royal  Italian  Mint  at  Rome. 

2  No  nitrous  fumes  should  be  present  in  the  nitric  acid  used  and  those  formed 
during  the  reaction  should  be  completely  expelled,  since  nitrous  fumes — and  nitric 
acid  itself  in  the  hot — decompose  thiocyanates. 

3  Gay-Lussac  :  Instruction  sur  I'essai  des  matures  d' argent  par  la  voie  humide,  Paris, 
Imprimerie  royale. 


282 


SILVER  ALLOYS 


at  each  end.  At  the  upper  end  is  fixed,  by  means  of  a  rubber  stopper,  a 
glass  basin  to  catch  the  overflow,  while  the  lower  end  is  connected  by  a 
rubber  tube  and  tap  with  the  vessel  containing  the  sodium  chloride  solution 
fixed  at  a  convenient  height.  The  pipette  is  filled  by  opening  the  tap  and 
allowing  the  liquid  to  flow  gently  over.  When  the  liquid  begins  to  overflow 
at  the  top,  the  latter  is  closed  by  means  of  the  index  finger  of  the  left  hand, 
while  the  tap  is  shut  and  the  rubber  tube  carefully  detached  with  the  left 
hand.  The  lower  end  is  then  touched  outside  with  a  dry  vessel  to  remove 
the  small  amount  of  adherent  liquid  and  the  bottle  placed  centrally  under 


V 


FIG.  24 


FIG.  25 


the  pipette.  The  finger  is  then  withdrawn  from  the  top  and  all  the  liquid 
flowing  in  a  continuous  jet,  but  not  the  drops  falling  subsequently,  allowed 
to  run  into  the  bottle. 

The  pipettes  should  be  kept  perfectly  free  from  grease  and,  before  use, 
should  be  washed  at  least  twice  with  the  solution  to  be  measured. 

3.  A  shaking  apparatus,  which  may  be  one  of  those  commonly  employed 
in  chemical  laboratories  for  bottles.     In  assayers'  laboratories  special  closed 
forms  of  apparatus  are  used  to  protect  the  bottles  from  the  action  of  the 
light.    They  take  10  bottles  at  a  time  and  are  often,  as  in  the  Mint  at  Rome, 
worked  electrically.     The  shaking  should  be  rapid  and  vigorous. 

4.  A  kind  of  tray  with  cells  for  carrying  10  bottles,  screened  from  the 
light,  from  one  part  to  another  of  the  laboratory. 

5.  A  water-bath  for  heating  the  bottles  during  the  attack  of  the  metal. 
Assaying  laboratories  have  also  a  suitable  bench  fitted  with  a  back  and 

a  raised  ledge  placed  against  a  window,  facing  north  if  possible.  On  the 
bench  the  sodium  chloride  solution  is  measured,  while  the  solutions  which 
have  already  cleared  are  arranged  on  the  ledge  to  receive  the  weaker  standard 


SILVER  ALLOYS  283 

salt  solution.  By  raising  each  test  separately  above  the  screen  so  that 
the  upper  part  becomes  directly  illuminated  it  is  easy  to  discern  the  cloud 
produced  by  the  new  addition  of  solution. 

Reagents.  i.  Standard  salt  solution,  100  c.c.  of  which  precipitates  almost 
completely  I  gram  of  pure  silver.  It  is  prepared  by  dissolving  5-4200 
grams  of  pure  sodium  chloride  to  i  litre  with  distilled  water  or  5-570  grams 
of  sea-salt,  dried  between  filter  papers,  to  I  litre  with  ordinary  water  1  and, 
in  the  latter  case,  filtering  the  solution. 

2.  Weak  standard  salt  solution,  one-tenth  as  strong  as  the  preceding 
solution,  from  which  it  may  be  prepared  by  dilution ;    or  0-5420  gram  of 
pure  sodium  chloride  may  be  dissolved  to  i  litre.     This  solution,  I  c.c.  of 
which  corresponds  with  o-ooi  gram  Ag,  is  stored  in  a  bottle  fitted  with  a 
rubber  stopper  traversed  by  a  pipette  graduated  from  i  to  5  c.c. 

3.  Pure  nitric  acid,  D  1-2,  free  from  chlorine. 

Standardisation  of  the  salt  solution,  i  gram  of  pure  silver  (fine  silver, 
see  preceding  method)  is  weighed  with  the  greatest  accuracy  z  and  heated 
in  a  water-bath  in  one  of  the  test  bottles  with  8-10  c.c.  of  nitric  acid  (D  1-2) 
until  the  metal  is  dissolved  and  the  red  vapours  have  disappeared.  After 
cooling,  the  neck^of  the  bottle  is  washed  with  a  few  drops  of  water  and  100 
c.c.  of  the  standard  salt  solution  introduced  by  means  of  one  of  the  pipettes 
described,  care  being  taken  that  only  the  liquid  fairing  in  a  continuous 
stream  enters  and  not  the  subsequent  drops.  The  bottle  is  then  stoppered 
and  shaken  for  about  10  minutes  in  the  shaking  apparatus,  the  precipitate 
clotting  and  the  liquid  becoming  quite  clear.  With  a  rapid  shake  the 
particles  of  precipitate  are  removed  from  the  upper  part  of  the  bottle,  the 
latter  being  then  placed  on  the  bench,  the  stopper  removed  and  i  c.c.  of 
the  weaker  standard  salt  allowed  to  flow  gently  down  the  side  of  the  bottle. 
After  4-5  minutes  the  bottle  is  raised  so  that  the  upper  portion  of  the  liquid 
becomes  illuminated,  fresh  precipitation  of  the  silver  in  the  form  of  a  cloud 
at  the  surface  of  the  liquid  being  usually  observed. 

The  solution  is  exact  when  this  cloud  is  barely  perceptible  and  when 
it  disappears  on  gently  shaking  the  liquid ;  if  there  is  too  much  cloud,  the 
standard  solution  must  be  corrected  by  addition  of  salt,  whilst,  if  no  cloud 
is  produced,  the  solution  must  be  diluted.  Only  the  first  case  will  be  con- 
sidered, as  the  second  may  be  reduced  by  suitable  dilution  to  the  first. 
When  the  addition  of  i  c.c.  of  the  weaker  standard  salt  produces  too  intense 
a  cloud,  the  bottle  is  shaken  in  the  apparatus  for  10  minutes  and,  after 
clearing,  treated  with  a  further  i  c.c.  of  the  weaker  salt.  This  process  is 
continued  until  such  an  addition  causes  either  no  further  precipitation  or 
only  a  scarcely  perceptible  cloud.  In  calculating  the  correction,  the  last 
c.c.  is  either  neglected  or  taken  as  only  0-5  c.c.  in  the  first  case,  but  must 
be  taken  into  account  in  the  second  case.  If,  for  instance,  the  complete 

1  In  assaying  laboratories  sea-salt  is  usually  employed  and  10  litres  of  solution 
prepared  at  a  time. 

a  To  facilitate  weighing,  strips  of  the  rolled  metal  weighing  more  than  i  gram  are 
placed  on  the  balance  pan,  the  excess  being  then  removed  first  with  metal  shears  and 
then  by  rubbing  one  of  the  strips  (the  largest)  held  in  flat-ended  tongs  against  a  very 
fine  file  until  perfect  equilibrium  of  the  balance  is  attained.  The  filed  piece  should 
be  dusted  with  a  brush  to  remove  any  adherent  filings. 


284  SILVER  ALLOYS 

precipitation  of  i  gram  of  fine  silver  requires  100  c.c.  of  the  standard  salt 
plus  3  c.c.  of  the  weaker  standard  salt  solution,  to  every  100  c.c.  of  the 
standard  salt  it  will  be  necessary  to  add  a  quantity  of  sodium  chloride 
corresponding  with  that  contained  in  3  c.c.  of  the  weaker  standard,  i.e., 
(0-000542  x  3)  gram  if  pure  salt  has  been  used,  or  (0-000557  X  3)  gram 
with  sea-salt.  After  this  new  quantity  of  salt  has  been  added  and  dissolved, 
the  resulting  solution  is  tested  to  ascertain  if  any  small  correction  is  still 
necessary. 

The  temperature  of  the  standard  solution,  corrected  in  this  way,  is 
noted.  Each  time  it  is  used,  it  should  be  well  shaken  to  render  it  homo- 
geneous. 

Actual  test.  We  will  suppose  that  the  preliminary  test  of  an  alloy  of 
silver  and  copper  by  Volhard's  method  gives  the  approximate  fineness  834. 
A  weight,  i-20i  gram,  is  taken,  this  containing  very  slightly  more  than  i 
gram  of  silver.  Two  pieces,  each  of  this  weight,  are  placed  in  two  of  the 
bottles  and  treated  with  8-10  c.c.  of  nitric  acid  (D  1-2)  with  the  precautions 
mentioned  above.  When  cold,  100  c.c.  of  the  standard  salt  solution  is 
run  into  each  bottle,  which  is  then  shaken,  the  further  procedure  being 
as  described  for  the  standardisation  of  the  salt  solution.  If,  in  addition 
to  the  100  c.c.  of  the  standard  salt  solution,  i  c.c.  of  the  weaker  standard 
is  required,  the  amount  of  the  silver  in  the  1-201  gram  of  the  sample  will 
be  I'OOi  gram,  the  fineness  of  the  alloy  being  833-4  (1201  : 1001  : :  1000  : 

833-4). 

To  obtain  greater  accuracy,  the  weaker  standard  salt  solution  may  be 
added  in  portions  of  0-2  c.c.  A  practised  observer,  however,  by  comparing 
the  intensity  of  the  cloud  given  by  the  check  with  that  given  by  the  sample, 
can  estimate  accurately  by  the  eye  o-i  c.c.  of  the  weaker  standard  salt 
solution.  In  special  works  dealing  with  this  subject,  tables  compiled  by 
Gay-Lussac  are  given  which  render  unnecessary  the  calculations.  If  it 
happens  that  the  addition  of  i  c.c.  of  the  weaker  standard  salt  produces 
no  cloud,  it  is  best  to  repeat  the  test  with  a  larger  quantity  of  the  sample. 

Gay-Lussac's  method,  although  expeditious,  is  undoubtedly  the  most  exact 
of  all  and  is  universally  employed  for  the  control  of  silver  coinage.  Naturally 
the  accuracy  of  the  results  depends  on  the  accuracy  of  the  weighing  and  par- 
ticularly on  the  accuracy  with  which  the  standard  solution  is  measured  (i  drop 
=  0-5  milligram  Ag).  It  is  necessary  also  to  allow  for  variations  of  temperature, 
since  at  different  temperatures  the  amount  of  sodium  chloride  contained  in 
100  c.c.  of  the  standard  solution  varies  appreciably  (i°  higher  or  lower  may 
introduce  an  error  of  about  0-2  in  the  fineness).  To  eliminate  this  cause  of 
error,  Gay-Lussac  tried  weighing  the  standard  solution  instead  of  measuring 
it,  but  found  this  procedure  so  much  less  expeditious  that  he  discarded  it  and 
compiled  a  table  giving  corrections  for  temperature.  In  practice  the  simplest 
means  of  avoiding  such  an  error  is  to  carry  out,  at  the  same  time  as  the  test 
on  the  alloy,  a  control  test  with  pure  silver. 

In  connection  with  this  method  it  is  also  to  be  borne  in  mind  that  silver 
chloride,  as  pointed  out  by  Mulder,1  is  not  absolutely  insoluble,  a  minimal 
quantity  remaining  in  solution  and  undergoing  precipitation  only  by  excess  of 
the  reagent.  Thus,  if  the  amount  of  sodium  chloride  exactly  sufficient  to 

1  Die  Silberprobiermethode. 


SILVER  ALLOYS  285 

precipitate  all  the  silver  has  been  added  to  a  solution  of  silver  in  nitric  acid, 
a  cloud  will  be  formed  in  the  liquid  by  addition  of  either  sodium  chloride  or 
silver  nitrate.  This  may  constitute  a  source  of  error  if,  as  Gay-Lussac  originally 
suggested,  a  weak  standard  silver  nitrate  solution  is  used  in  cases  where  the 
amount  of  sodium  chloride  added  is  in  excess  with  respect  to  the  silver  dissolved. 
On  this  account  Stas  *  proposed  a  modification  of  the  Gay-Lussac  method,  this 
consisting  in  the  replacement  of  the  sodium  chloride  solutions  by  the  correspond- 
ing hydrobromic  acid  solutions,  silver  bromide  being  perfectly  insoluble.  This 
method,  which  is  used  in  the  Brussels  mint,  is  rather  more  delicate  than  that 
of  Gay-Lussac,  but  it  requires  perfect  expulsion  of  the  nitrous  vapours  and 
special  precautions  to  prevent  access  of  light  to  the  tests,  etc. 

If,  however,  the  Gay-Lussac  method  is  carried  out  as  described  above,  the 
weak  standard  silver  nitrate  being  suppressed  and  identical  conditions  employed 
in  both  control  test  and  that  on  the  sample,  all  causes  of  error  are  eliminated. 

As  regards  the  influence  of  extraneous  metals,  it  must  be  borne  in  mind  that 
mercury  affects  the  accuracy  of  the  results,  as  it  also  is  precipitated  as  mercurous 
chloride  ;  when  this  metal  is  present,  it  is  expelled  by  heating  the  alloy  to  fusion 
in  a  graphite  crucible.  When  tin,  antimony  or  bismuth  is  present,  an  opalescent 
liquid  is  obtained  in  which  it  is  difficult  to  observe  the  formation  of  cloudiness. 
In  presence  of  antimony  or  bismuth  a  little  tartaric  acid  (1-2  grams)  is  added, 
whilst  when  the  alloy  contains  tin  or  a  large  proportion  of  lead,  it  is  advisable 
to  dissolve  it  in  sulphuric  acid.  Further,  gold  in  proportion  exceeding  a  fineness 
of  60-80  (6-8%)  influences  the  results  as  it  withholds  a  little  silver.  Copper  in 
amount  greater  than  50%  gives  coloured  solutions,  which  render  observation 
difficult. 

2.  Determination  of  the  Gold. — In  a  flask  with  a  long,  narrow  neck, 
10  grams  of  the  sample  are  dissolved  in  80-100  c.c.  of  nitric  acid  (D  1-2), 
the  solution  being  decanted  off  and  the  residue  again  boiled  with  nitric 
acid,  which  is  also  decanted.     The  residue  is  washed  repeatedly  with  hot 
water  by  decantation  and  the  undissolved  gold  remaining  as  a  black  powder 
collected  in  a  refractory,  unglazed  crucible  (see  Gold  and  its  Alloys — Quarta- 
tion),  dried,  ignited  and  weighed. 

3.  Detection  of  Tin,  Antimony,  Copper,  Bismuth  and  Lead. — 
5  grams  of  the  sample  are  treated  with  nitric  acid  (D  1-2).     In  presence 
of  tin  or  antimony,  the  liquid  is  opalescent  or  contains  a  slight  white  pre- 
cipitate.    If  the  filtered  solution  is  rendered  alkaline  with  ammonia,  it 
will  turn  more  or  less  intensely  blue  if  copper  is  present,  whilst  a  flocculent 
precipitate  will  form  in  presence  of  bismuth  or  lead,  which  may  be  identified 
by  the  usual  means. 


*** 


Natural  and  crude  silver  often  contains  small  quantities  of  gold,  lead,  mercury, 
copper,  antimony,  arsenic  and  sometimes  selenium  and  bismuth.  The  presence 
of  bismuth  is  extremely  harmful,  alloys  made  with  silver  containing  only  traces 
of  bismuth  being  rough  and  brittle.  Refined  silver  is  usually  very  pure,  the 
best  qualities  containing,  on  the  average,  99-9%  Ag. 

Silver  is  used  especially  alloyed  with  copper  for  jewellery,  coinage,  etc.  The 
legal  standard  for  Italian  5-lire  pieces  is  900  fine  with  a  variation  of  2  either  way, 
and  that  for  plate  is  usually  900  fine,  and  that  for  jewellery  800  or  even  less — 
down  to  500  fine. 

1  De  Koninck  :    TraM  de  chimie  analytique,  II,  p.  561. 


286  ALLOYS  OF  GOLD  AND  COPPER 


GOLD    AND    ITS    ALLOYS 

The  more  important  commercial  products  are  :  gold  in  bars,  sheet, 
granules,  powder,  etc.,  and  its  alloys  with  copper  alone  and  with  silver  and 
copper. 

GOLD 

The  essential  determination  to  be  carried  out  on  the  metal  is  that  of 
the  gold,  the  fineness  being  the  amount  of  gold  per  1000  parts  of  the  metal. 
This  determination  is  made  as  in  alloys  of  gold  and  copper  (q.v.). 


ALLOYS  OF  GOLD  AND  COPPER 

The  most  important  determination  is  : 

1.  Determination  of  the  Gold. — By  cupellation  in  presence  of  lead, 
the  gold  is  separated  from  copper  and  other  ordinary  metals  with  which 
it  may  be  alloyed,  but  not  from  silver,  which  resembles  gold  in  being  un- 
oxidisable  at  the  highest  temperatures.  To  eliminate  the  silver,  which 
always  accompanies  gold  in  larger  or  smaller  proportion,  it  is  necessary  to 
treat  with  acid.  Experience  has  shown  that,  for  the  complete  elimination 
of  the  silver,  the  latter  must  be  in  considerable  excess,  namely,  about  3 
parts  to  i  part  of  gold.  It  is,  therefore,  necessary,  before  cupellation  to 
add  silver  to  make  this  relation  hold.  The  assay  of  gold  hence  comprises 
two  distinct  operations  : 

(1)  Cupellation  in  presence  of  lead  and  silver  to  eliminate  the  base 
metals  and  to  form  the  alloy  of  gold  and  silver  in  the  above  proportions, 
an  operation  termed  inquartation,  since  the  gold  constitutes  about  one- 
fourth  of  the  resulting  alloy. 

(2)  Treatment  of  the  latter  with  acid  to  remove  the  silver,  this  operation 
being  known  as  parting. 

To  calculate  the  quantities  of  silver  and  lead  to  be  used  in  the  cupellation 
the  gold  content  of  the  sample  must  be  known  approximately.  It  is  neces- 
sary, therefore,  to  make  a  preliminary  assay  and  this  is  usually  done  by 
means  of  the  touchstone. 

PRELIMINARY  TOUCHSTONE  ASSAY.  This  consists  in  tracing  a  streak 
with  the  sample  on  the  touchstone  beside  streaks  traced  with  gold-copper 
alloys  of  known  fineness  and  comparing  the  colours  of  the  streaks  before  and 
after  treatment  with  acid. 

This  test  requires  : 

(1)  The  touchstone.     A  good  stone  should  be  unattackable  by  acid  and 
should  be  of  a  uniform  black  colour,  hard,  of  fine  grain  and  opaque  surface. 

(2)  The  needles,  consisting  of  small,  thick  discs  or  plates  of  gold-copper 
alloys  of  definite  fineness,  fixed  to  metallic  handles  on  which  the  fineness  is 
marked. 

(3)  The  acids,  which  vary  in  composition  according  to  the  fineness  of 
the  alloy  to  be  tested.     The  acids  generally  used  are  the  so-called  500  acid 


ALLOYS  OF  GOLD  AND  COPPER  287 

for  finenesses  between  350  and  500,  the  750  acid  for  finesses  500-750,  and 
the  900  acid  for  finenesses  above  750.     The  compositions  of  these  acids  are  : 


500  acid. 
Nitric  acid  (D  1-384),  40 

c.c. 
Hydrochloric      acid      (D 

1-19),  0-5  c.c. 
Distilled  water,  20  c.c. 


750  acid. 
Nitric  acid  (D  i'346),  98 


c.c. 


Hydrochloric     acid      (D 
1-171),  2  c.c. 


900  acid. 
Nitric  acid  (D  1-384),  40 


c.c. 


Hydrochloric     acid      (D 
1-19),  5  c.c. 


Distilled  water,  25  c.c.      j  Distilled  water,   15  c.c. 


The  procedure  consists  in  rubbing  the  sample  on  the  stone  so  as  to  leave 
a  sharp  line  3-4  mm.  wide  and  15-20  mm.  long,  and  quite  close  to  this, 
two  streaks  with  two  needles  one  less  and  the  other  more  fine  than  the 
external  characters  of  the  alloy  would  indicate  for  it.  The  streaks  are 
observed  in  the  light  and  compared.  A  little  of  the  acid  corresponding 
with  the  fineness  of  the  comparison  needles  is  then  rubbed  with  a  glass 
rod  over  the  streaks,  which  are  then  compared,  dried  with  absorbent  paper, 
again  treated  with  acid,  again  dried,  and  the  residues  of  gold  on  the  stone 
compared.  From  the  colour  of  the  streaks  before  treatment  with  acid 
and  the  intensity  of  those  remaining  after  the  action  of  the  acid,  the  approxi- 
mate fineness  of  the  alloy  is  judged.  If  the  streak  left  by  the  sample  is 
not  comparable  with  those  of  the  needles,  the  test  must  be  repeated  with 
needles  of  higher  or  lower  fineness. 

ACTUAL  TEST.  Apparatus  and  reagents,  (i)  A  muffle  furnace,  cupels, 
and  a  thermo-electric  couple  like  that  used  in  the  cupellation  of  silver  (q.v.}. 

(2)  Silver  of  999  fineness  absolutely  free  from  gold,  and  lead  which  need 
not  be  free  from  silver. 

(3)  Highly  resistant  pear-shaped  flasks  with  stout,  very  long  necks  (assay 
flasks)  and  a  crucible  of  very  fine  refractory  earth  or  of  unglazed  porcelain 
or  graphite. 

Amounts  of  silver  and  lead  to  be  used  in  the  cupellation.  The  assay  of 
the  gold  is  carried  out  in  duplicate  on  0-5  gram  of  the  sample,  and  the  amount 
of  silver  to  be  added  for  the  inquartation  is  about  three  times  (more  exactly 
2-5  times)  that  of  the  gold.  Thus,  if  the  touchstone  assay  indicates  an 
approximate  fineness  of  900,  the  amount  of  silver  to  be  added  to  each  o'5 
gram  of  the  alloy  is  0-9  X  2-5  X  0-5  =  1-125  gram.  The  silver,  which  is 
weighed  to  the  nearest  centigram,  should  be  in  sheet  which  is  not  too  thin, 
so  that  the  piece  used  in  each  case  forms  two  squares  of  0-5  cm.  side. 

The  amount  of  lead  required  is  also  related  to  the  fineness  of  the  alloy 
and  is  given  by  the  following  table  : 

Fineness  of  Amount  of  lead  (grams)  required 

the  sample.  per  0-5  gram  of  sample. 

1000  .     .     .         *    .  .  0-5 

900  __..-.  5-0 

800  8-0 

700  ......  ii-o 

600  ......  12-0 

500  ......  13-0 

400-100    ......  17-0 

Procedure.     The  gold  is  sampled  in  the  manner  indicated  for  silver  (q.v.), 


288          ALLOYS  OF  GOLD  AND  COPPER 

reduced  to  sheet  and  two  test-pieces  of  0-5  gram  each  weighed  with  the 
greatest  exactitude  *  if  possible,  each  piece  should  consist  of  a  single  square 
of  about  0-5  cm.  side.  This  is  placed  between  the  two  pieces  of  silver  foil 
and  the  whole  wrapped  in  a  piece  of  white  paper  or  of  thin  lead  foil  (allowing 
for  the  weight  in  calculating  the  lead  to  be  taken)  and  placed  in  the  tray 
beside  the  corresponding  quantity  of  lead. 

Meanwhile  the  furnace  is  started  and  the  cupels,  from  which  the  dust 
has  been  blown,  introduced.  In  gold  assay  there  is  no  danger  of  sensible 
loss  owing  to  volatilisation,  so  that  a  rather  higher  temperature  than  for 
silver  may  be  used.  According  to  T.  K.  Rose,1  the  most  suitable  mean  tem- 
perature is  about  1070°,  each  5°  above  this  causing  a  loss  of  o-oi  on  the  fine- 
ness. When  the  temperature  indicated  is  reached,  each  cupel  is  charged 
with  the  weighed  quantity  of  lead,  which  rapidly  melts,  becomes  covered 
with  a  layer  of  oxide  and,  after  a  few  instants,  becomes  uncovered,  i.e., 
shining.  With  great  care,  to  avoid  spurting,  the  little  parcel  of  sample 
and  silver  is  placed  in  the  cupel.  The  phenomena  of  the  cupellation  are 
identical  with  those  observed  with  silver  ;  after  some  time  the  agitation 


FIG.  26  FIG.  27 

on  the  surface  is  observed,  then  the  iridescence,  and  finally  the  bright  flashing. 
The  cupels  are  then  moved  towards  the  door  of  the  muffle,  allowed  to  cool 
somewhat  and  withdrawn,  the  buttons  being  detached  with  a  suitable 
utensil.  With  successful  cupellation,  the  buttons  should  be  hemispherical, 
shining  and  white  at  the  upper  part  and  opaque  white  at  the  lower.  The 
button  is  held  in  strong  pincers,  the  edges  struck  with  a  hammer  and  the 
flat  part  freed  from  cupel  dust  by  means  of  a  stiff  brush.  It  is  then  placed 
on  a  clean  anvil  and  struck  alternately  on  the  sides  and  on  the  flat  part  so 
as  to  give  it  a  somewhat  elongated  form  and  is  next  reheated  to  redness  by 
leaving  it  for  a  short  time  on  a  cupel  in  the  front  part  of  the  muffle.  When 
cool,  it  is  rolled  to  obtain  a  strip  (fillet)  about  0-5  mm.  thick  and  of  the  form 
shown  in  Fig.  26.  This  strip,  bent  in  two  in  a  smooth  curve,  is  again  reheated 
to  redness  for  4-5  minutes  on  a  cupel.  When  cold,  it  is  twisted  into 
a  spiral  round  a  glass  rod  so  as  to  obtain  almost  a  tube  about  0-5  cm.  wide 
(cornet),  care  being  taken  that  the  rolls  of  the  spiral  do  not  touch  (Fig.  27)  ; 
this  is  then  subjected  to  the  operation  of  parting. 

Parting.  Each  of  two  assay  flasks  is  charged  with  25-30  c.c.  of  nitric 
acid  (D  3/2)  absolutely  free  from  chlorine,  nitrous  fumes  and  selenic  acid, 
this  being  heated  to  boiling  and  the  two  cornets  introduced.  The  heating 
is  continued  so  as  to  maintain  the  liquid  in  gentle  ebullition  for  ten  minutes 
after  evolution  of  nitrous  vapours  ceases.2  After  a  short  rest,  the  liquid 

1  Journal  of  the  Chemical  Society,  1893,  LXIII,  p.  707. 

2  In  assay  laboratories,  there  is  usually  a  special  apparatus  for  the  elimination  of 
the  nitrous  vapours  and  acid  fumes  evolved  during  the  treatment  of  the  cornet  with 
nitric  acid.     It  consists  of  one  or  two  series  of  8-10  small  bunsen  burners,  over  which 
are  placed  as  many  flasks  with  their  inclined  necks  projecting  through  a  rectangular 
aperture  into  a  space  communicating  with  an  efficient  draught  chamber.     Between 


ALLOYS  OF  GOLD  AND  COPPER          289 

is  carefully  decanted  off  as  completely  as  possible  without  allowing  the 
cornet  to  escape.  The  residue  is  again  boiled  for  10  minutes  with  20  c.c. 
of  nitric  acid  (D  1-3).  With  the  more  concentrated  acid  the  boiling  is  less 
regular  and  dangerous  bumping  may  occur,  and  some  authorities  recommend 
the  addition  of  a  scrap  of  wood  charcoal  or  a  completely  charred  pepper- 
corn. After  this  second  portion  of  acid  has  been  decanted  off,  a  further 
quantity  of  20  c.c.  of  nitric  acid  (D  1-3)  is  added  and  boiled  for  10  minutes 
to  remove  the  last  traces  of  silver.  When  this  last  acid  together  with  the 
piece  of  charcoal  have  been  removed,  the  cornet  is  washed  with  two  quan- 
tities of  30-40  c.c.  of  boiling  water,  the  flask  being  subsequently  filled 
completely  with  cold  distilled  water.  The  mouth  of  the  flask  is  then  closed 
by  means  of  an  inverted  crucible  of  refractory  earth  or  unglazed  porcelain, 
which  is  pressed  firmly  on  while  the  flask  is  inverted.  A  little  water  descends 
into  the  crucible  and  forms  a  hydraulic  seal,  while  the  brittle  and  slender 
cornet  slowly  falls  to  the  bottom  of  the  crucible.  After  some  time,  when 
any  small  fragments  detached  from  the  cornet  have  been  deposited,  the 
flask  is  gradually  raised  to  the  edges  of  the  crucible,  displaced  a  little  laterally 
and  with  a  rapid  movement  brought  into  an  erect  position.  The  water  is 
decanted  from  the  crucible  which  is  dried  on  the  platform  of  the  furnace 
and  subsequently  heated  to  redness  in  the  muffle  for  2-3  minutes.  Under 
the  influence  of  the  heat  the  cornet  contracts  to  about  one-third  of  its  original 
volume  and  assumes  a  golden- yellow  metallic  appearance.  When  cold,  the 
two  cornets  are  weighed  together,  the  total  weight  giving  directly  the 
fineness  of  the  sample  ;  the  weights  of  the  separate  cornets  should  not 
differ  by  more  than  0-5  milligram. 

In  the  assay  of  gold  by  cupellation,  small  losses  occur  (according  to 
Rose,  0-5-1  on  the  fineness)  owing  partly  to  volatilisation  of  the  gold  and 
partly  to  imbibition  by  the  cupel.  This  slight  loss  is,  however,  compen- 
sated by  the  small  amount  of  silver  (0-75-1  one-thousandth)  which  always 
remains  with  the  gold  in  spite  of  the  different  treatments  with  nitric  acid. 
Thus,  according  to  Rose,  if  the  operation  is  properly  conducted,  the  error 
should  not  exceed+o-2  per  thousand.  The  losses  by  volatilisation  increase 
with  the  amount  of  lead  used  and,  consequently,  with  diminution  of  the 
proportion  of  gold  in  the  alloy  *  on  this  account,  Riche  advises  the  omission 
of  the  third  treatment  with  nitric  acid  in  the  case  of  gold-copper  alloys  of 
lower  fineness  than  800.  In  some  laboratories  the  small  errors  are  esti- 
mated by  making  a  control  assay  with  pure  gold  1  and  pure  copper  in  about 
the  same  proportions  as  in  the  sample,  the  mixture  being  cupelled  with 
the  same  quantities  of  silver  and  lead,  and  the  parting  carried  out  under 
the  same  conditions.  In  assaying  commercial  fine  gold  Riche  advises  the 
addition  of  20  per  thousand  of  copper  to  prevent  brittleness  in  the  button 
obtained. 

As  regards  extraneous  metals,  small  quantities  of  platinum  render  the 

one  series  and  the  next  are  the  bottles  with  the  nitric  acid  and  the  distilled  water  and 
below  them  three  bottles  to  receive  :  (i)  the  first  two  lots  of  acid,  rich  in  silver  nitrate, 
(2)  the  third  lot  of  acid,  and  (3)  the  wash  water. 

1  For  the  preparation  of  pure  gold,  see  Roberts-Austen  :  Fourth  Mint  Report, 
London,  1873,  46. 

A.C.  19 


290  ALLOYS   OF  GOLD,   SILVER  AND   COPPER 

button  wrinkled  and  crystalline,  but  less  than  2%  of  platinum  does  not 
influence  the  results  since,  in  presence  of  silver  and  gold,  it  then  dissolves 
in  the  nitric  acid.  If  the  platinum  is  present  in  higher  proportions  (up 
to  10-15%),  the  cupellation  is  carried  out  at  a  higher  temperature  in  presence 
of  twice  as  much  lead  as  is  indicated  in  the  table  ;  after  the  parting  the 
cornets  are  weighed,  again  subjected  to  inquartation  with  silver  and  20 
per  1000  of  copper  and  again  parted  with  acid  of  D  1-3,  these  operations 
being  repeated  until  the  cornets  are  of  constant  weight. 

Palladium  has  no  injurious  effect,  since  it  dissolves  completely  in  nitric 
acid. 

Indium  causes  the  formation  of  black  spots  on  the  button,  these  remain- 
ing even  after  parting.  If  the  gold  is  dissolved  in  aqua  regia,  the  indium 
remains  undissolved  and  may  be  collected  and  weighed. 


ALLOYS    OF    GOLD,    SILVER    AND    COPPER 

In  the  assay  of  these  alloys,  three  cases  are  distinguished : 

(1)  Rich  alloys,  in  which  the  proportion  of  gold  to  silver  is  higher  than 

1:3- 

(2)  Medium  alloys,  with  a  proportion  of  about  1:3. 

(3)  Poor  alloys,  with  a  proportion  less  than  1:3.     The  assay  of  these 
alloys  includes  two  operations  : 

(1)  Cupellation,  which  gives  the  gold  and  silver  together. 

(2)  Parting,  which  gives  the  gold  alone. 

Preliminary  test.  In  presence  of  silver  the  touchstone  assay  does  not 
always  give  reliable  results  (the  presence  of  silver  is  easily  detected  by  the 
formation  of  a  slight,  white  precipitate  on  the  streak  when  treated  with 
the  acid),  so  that  a  preliminary  assay  by  cupellation  is  advisable.  This  is 
made  with  0-250  gram  of  the  sample  and  4-8  grams  of  lead,  according  to 
the  supposed  richness  in  copper,  the  button  of  gold  and  silver  being  weighed  ; 
the  weight  of  the  sample,  less  that  of  the  button,  gives  approximately  that 
of  the  copper.  The  button  is  then  rolled,  the  strip  treated  with  nitric  acid 
and  the  remaining  gold  weighed  ;  the  proportion  of  silver  is  then  found  by 
difference. 

I.  RICH  ALLOYS,  (a)  Determination  oj  the  gold.  This  is  carried  out  on 
two  separate  portions  of  0-5  gram  under  the  conditions  given  for  the  deter- 
mination of  gold  in  gold-copper  alloys.  The  inquartation  silver  must  be 
diminished  in  amount  by  the  approximate  silver  content  indicated  by  the 
preliminary  assay  (see  p.  287).  The  amount  of  lead  required  is  based  on 
the  total  fineness  and  on  the  ratio  between  the  gold  and  silver  (see  later : 
Medium  Alloys). 

(b)  Determination  of  the  silver.  0-5  gram  of  the  alloy  is  cupelled  with 
the  quantity  of  lead  used  for  the  determination  of  the  gold,  the  resulting 
button  representing  gold  and  silver  together  ;  the  latter  is  thus  found  by 
difference. 

If  the  alloy  consists  of  gold  and  silver  alone,  2o-thousandths  of  copper 
must  be  added  to  the  test.  If  the  gold  fineness  is  less  than  800,  the  third 
treatment  with  acid  is  omitted. 


ALLOYS  OF  GOLD,   SILVER  AND  COPPER  291 

II.  MEDIUM  ALLOYS,     (a]  Determination  oj  the  gold  and  silver.    Two 
quantities  of  0-5  gram  are  cupelled  under  the  conditions  given  for  gold- 
copper  alloys  but  at  a  somewhat  higher  temperature,  and  with  no  added 
silver.     The  amount  of  lead  to  be  added  is  calculated  on  the  basis  of  the 
total  gold  and  silver  contents,   one-fourth  of  the  quantity  indicated  by 
the  table  for  the  cupellation  of  gold  and  three-fourths  of  that  given  for  the 
cupellation  of  silver,  being  taken. 

Example  :  If  the  preliminary  assay  gives  Au  220  and  Ag  680  per  1000, 
the  total  fineness  is  900.  For  this  value  the  table  for  the  cupellation  of 
gold  would  indicate  5  grams  of  lead,  so  that  1-25  is  taken,  and  the  table 
for  the  cupellation  of  silver  would  indicate  3-5  grams  of  lead,  so  that  2 '6 
(=  3  x  3-5/4)  is  taken  ;  the  total  amount  of  lead  taken  is  thus  1-25  + 
2-6  =  3-85  grams. 

The  buttons  obtained  are  weighed  together  and  subjected  to  parting. 
The  gold  is  given  by  the  total  weight  of  the  two  cornets  and  the  silver  by 
difference  (button  minus  gold). 

III.  POOR  ALLOYS.     Two  o'5  gram  samples  are  cupelled  as  described 
for  the  cupellation  of  silver  and  with  the  amounts  of  lead  there  prescribed  ; 
the  temperature  is,  however,  kept  somewhat  higher,  especially  if  the  fineness 
of  the  gold  exceeds  50  per  thousand.     The  sum  of  the  weights  of  the  two 
buttons  gives  the  silver  +  gold.     To  separate  the  silver,  the  buttons  are 
parted,  bearing  in  mind  that,  if  the  fineness  of  the  gold  is  not  more  than 
5  per  1000,  the  two  buttons  should  be  parted  in  the  same  flask,  and  that, 
for  values  exceeding  20  per  1000,  the  buttons  should  be  rolled  and  reheated 
at  low  redness  ;    further,  that,  before  decanting  the  acid  from  the  flask, 
the  liquid  should  be  given  a  rotary  motion,  so  that  the  gold  dust  collects 
at  the  bottom ;  that  the  third  treatment  with  acid  should  be  omitted  and 
that  great  care  is  necessary  to  avoid  loss  during  the  descent  of  the  gold 
dust  into  the  crucible. 

If  the  gold  content  does  not  exceed  60-80  per  1000,  the  silver  may  be 
determined  with  greater  exactitude  by  the  Gay-Lussac  method  (see  Silver 
and  its  Alloys). 

* 

*  * 

Crude  gold  contains  considerable  quantities  of  impurities,  especially  silver, 
copper,  lead,  bismuth,  tin,  antimony,  arsenic,  etc.  Thus,  gold  obtained  by 
amalgamation  varies  from  865  to  970  fine,  whereas  that  given  by  the  Siemens 
process  has  a  fineness  of  890-900  and  contains,  besides  silver,  only  traces  of 
copper  and  lead  ;  gold  precipitated  by  zinc  is  600-700  fine  and  contains  con- 
siderable proportions  of  zinc,  lead,  iron  and  copper. 

Refined  gold  reaches  the  fineness  993-999,  but  always  contains  small  quan- 
tities of  silver. 

Gold  is  used  more  especially  alloyed  with  copper  for  jewellery,  coinage, 
medals,  etc.  The  legal  fineness  of  the  Italian  gold  coinage  is  900  Jh  i  and  that 
of  British  coinage  916-66.  With  jewellery,  plate,  etc.,  the  fineness  may  vary 
from  920  to  500. 

Gold-silver  and  gold-silver-copper  alloys  are  also  largely  used,  more  especially 
to  obtain  special  effects  in  articles  of  jewellery  (green  gold  :  750  Au,  250  Ag  ; 
red  gold  :  750  Au,  200  Ag,  50  Cu  ;  white  English  gold  :  750  Au,  170  Ag,  80  Cu, 
etc.). 


292  METALLIC  COATINGS 

METALLIC  COATINGS 

Many  metallic  objects  are  coated,  either  to  render  them  more  resistant 
to  the  action  of  external  agencies  or  to  enhance  their  appearance,  with 
more  or  less  thin  layers  of  other  metals  or  of  oxides.  These  coatings  are 
easy  to  characterise  by  the  tests  given  below. 


GOLD-PLATING 
(Gilding) 

1.  Technical  Test. — The  surface  of  the  object  is  rubbed  repeatedly 
with  a  small  piece  of  very  fine  glass  paper  (No.  ooo)  so  as  to  concentrate  any 
gilding  at  one  point  of  the  glass  paper.     This  point  is  then  treated  with  a 
drop  of  cone,  nitric  and  one  or  two  drops  of  cone,  hydrochloric  acid  and 
warmed  gently  over  a  very  small  flame  until  the  metal  is  dissolved.     The 
solution  is  then  washed  into  a  test-tube  with  1-2  c.c.  of  water,  the  liquid 
being  filtered  if  turbid  and  heated  with  either  an  equal  volume  of  fresh 
sulphur  dioxide  solution  or  a  few  drops  of  fresh  stannous  chloride  solution. 
In  presence  of  gold,  a  violet  red,  varying  coloration  is  observed  owing  to 
the  formation  of  purple  of  Cassius 

2.  Test  for  Small  Objects. — The  sample,  or  part  of  it,  or  a  number  of 
small  pieces,  according  to  circumstances,  are  heated  on  the  water- bath  with 
nitric  acid  diluted  with  an  equal  volume  of  water.     When  the  attack  of  the 
common  metal  is  complete,  the  liquid  is  filtered  through  a  small  filter  and 
the  residue  washed  thoroughly  with  hot  water.    The  filter  is  then  incinerated 
in  a  porcelain  dish  or  crucible  and  the  ash  treated  with  2  drops  of  cone, 
hydrochloric  acid  and  i  drop  of  cone,  nitric  acid  and  evaporated  to  dryness 
on  a  water-bath  until  the  excess  of  acid  is  entirely  expelled.     When  cold, 
the  residue  is  taken  up  in  about  2  c.c.  of  distilled  water  and  filtered,  the 
filtrate  being  heated  to  boiling  with  an  equal  volume  of  sulphur  dioxide 
solution  or  of  a  saturated  oxalic  acid  solution  or  a  few  drops  of  stannous 
chloride  solution.     If  gold  is  present,  the  characteristic  violet- red  coloration 
of  purple  of  Cassius  is  observed. 

3.  Test  for  Large  Objects. — After  removal  of  any  organic  matter, 
the  surface  is  scraped  with  a  penknife  and  the  scrapings  submitted  to  the 
preceding  test. 

SILVER-PLATING 

1.  Technical  Test. — The  article  to  be  tested,  freed  from  grease,1  is 
touched  with  a  drop  of  cone,  nitric  acid  and  the  latter  absorbed  by  a  strip 
of  filter-paper.  The  spot  is  then  treated  with  a  drop  of  formaldehyde  solution 
(commercial  formalin)  and  a  drop  of  20%  sodium  hydroxide  solution.  In 
presence  of  silver,  a  blackish  spot  of  reduced  silver  forms  either  immediately 
or  after  some  time. 

1  Sometimes  objects  are  covered  with  a  varnish  which  has  nitro-  or  acetyl-cellulose 
as  its  base  and  can  be  removed  only  mechanically. 


NICKEL-PLATING  293 

2.  Test  for  Small  Articles. — After  being  freed  from  grease,  the  article 
or  part  of  it  or  a  number  of  small  pieces,  are  treated  with  8-10  drops  of  a 
mixture  of  9  vols.  of  cone,  sulphuric  acid  with  I  vol.  of  cone,  nitric  acid — a 
mixture  which  readily  dissolves  the  superficial  silver  but  attacks  the  metal 
underneath  either  not  at  all  or  but  little.     When  the  attack  is  over,  the 
acid  is  decanted  into  a  test-tube,  mixed  with  2-3  c.c.  of  water,  filtered  if 
necessary  and  divided  into  two  portions.     To  one  of  these  are  added  1-2 
drops  of  dilute  hydrochloric  acid,  which  are  allowed  to  flow  gently  down 
the  wall  of  the  tube  and  form  a  layer  on  the  surface  of  the  sulphuric  acid 
solution.     If  silver  is  present,  a  more  or  less  distinct  milkiness  is  observed 
— best  by  comparison  with  the  other  portion — at  the  surface. 

3.  Test  for  Large  Articles. — In  general  the  technical  test  (see  above) 
is  applicable  in  this  case.     If,  however,  the  surface  or  form  of  the  object 
renders  this  difficult  the  surface  or  a  few  scrapings  may  be  treated  with 
nitric  acid  diluted  with  an  equal  volume  of  water,  care  being  taken  to  stop 
the  action  as  soon  as  the  superficial  silver  coloration  disappears.     The 
nitric  acid  solution  is  then  decanted  into  a  dish  and  evaporated  to  dryness 
with  a  drop  of  dilute  hydrochloric  acid  on  a  water-bath.     The  residue  is 
taken  up  in  hot  water,  acidified  with  nitric  acid  and  filtered  through  a  small, 
very  compact  filter,  which  is  repeatedly  washed  with  hot  water.     A  small 
quantity  of  hot,  dilute  ammonia  is  then  passed  a  number  of  times  through 
the  filter  and  the  ammoniacal  solution  divided  into  two  parts,  one  of  which 
is  made  faintly  acid  with  nitric  acid.     In  presence  of  silver  a  slight  precipi- 
tate or  a  more  or  less  marked  milkiness  is  observed. 


NICKEL-PLATING 

1.  Technical  Test. — The  surface  of  the  article  is  treated  with  a  drop 
of  cone,  hydrochloric  acid,  a  crystal  of  methylamine  hydrochloride  being 
placed  close  by  and  heat  applied .     In  presence  of  nickel,  the  place  attacked 
by  the  acid  exhibits  a  blue  spot  which  disappears  on  cooling. 

2.  Dimethylglyoxime    Test    (highly    sensitive). — After    being    freed 
from  grease,  the  surface  of  the  object  is  moistened  with  one  or  two  drops 
of  nitric  acid  diluted  with  an  equal  volume  of  water,  the  acid  being  sub- 
sequently washed  into  a  test-tube,  rendered  alkaline  with  ammonia,  heated 
to  boiling,  filtered  if  necessary  and  treated  with  two  or  three  drops  of  i% 
alcoholic  dimethylglyoxime  solution.     In  presence  of  nickel,  a  red  precipitate 
or  at  least  a  pink  coloration  is  formed. 

If  this  test  is  applied  to  an  object  of  copper  or  brass,  a  little  of  the  latter 
in  the  solution  would  give  a  brown  coloration  and  thus  mask  the  nickel 
reaction.  In  such  case,  after  addition  of  the  glyoxime  and  gentle  heating, 
the  liquid  is  filtered  ;  if  nickel  is  present,  a  slight  red  precipitate  will  remain 
on  the  filter.  A  better  method  to  follow  under  these  circumstances  con- 
sists in  acidifying  the  ammoniacal  solution  with  hydrochloric  acid,  pre- 
cipitating the  copper  by  means  of  hydrogen  sulphide,  filtering,  eliminating 
the  excess  of  hydrogen  sulphide,  rendering  slightly  ammoniacal,  filtering 
if  necessary,  and  then  adding  the  alcoholic  dimethylglyoxime. 


294  TIN-PLATING—ZINC-PLATING—LEAD-PLATING 


TIN-PLATING 

The  surface  of  the  object  or  scrapings  from  it  are  treated  with  hydro- 
chloric acid  diluted  with  an  equal  volume  of  water  and  gently  heated.  The 
liquid  is  filtered  and  treated  with  a  drop  of  mercuric  chloride  solution,  a 
white  or  grey  precipitate  of  calomel  or  metallic  mercury  being  formed  in 
presence  of  tin. 

ZINC-PLATING 

The  surface  is  heated  gently  with  dilute  sulphuric  acid  and  the  solution 
transferred  to  a  beaker  and  treated  with  hydrogen  sulphide.  The  filtered 
liquid  is  freed  from  the  excess  of  hydrogen  sulphide,  treated  with  a  little 
ammonium  chloride,  rendered  faintly  alkaline  with  ammonia,  boiled,  and 
again  filtered.  To  the  filtrate,  acidified  with  acetic  acid,  potassium  ferro- 
cyanide  is  added.  In  presence  of  zinc,  a  dirty  white  flocculent  precipitate 
forms  either  immediately  or  after  some  time. 


LEAD -PLATING 

Scrapings  of  the  surface  are  treated  in  a  dish  with  nitric  acid,  evaporated 
to  dryness  and  taken  up  in  a  few  drops  of  water.  The  solution  is  tested 
for  lead  by  means  of  potassium  chromate  or  iodide. 


ALUMINIUM -PLATING 

The  surface,  or  scrapings  of  it,  are  heated  with  10%  sodium  hydroxide 
solution.  The  liquid  is  diluted  somewhat,  filtered,  acidified  with  hydro- 
chloric acid  and  made  alkaline  with  ammonia.  A  white  gelatinous  pre- 
cipitate is  formed  in  presence  of  aluminium. 


COPPER-PLATING 
(on  Iron) 

The  object  or  part  of  it  is  treated  in  the  cold  with  cone,  nitric  acid, 
which  dissolves  the  copper  but  scarcely  affects  the  iron.  The  solution  is 
decanted  off,  diluted  and  tested  for  copper  with  ammonia. 

BRASS -PLATING 

The  surface  is  treated  with  nitric  acid  diluted  with  an  equal  volume  of 
water,  the  liquid  being  filtered  and  rendered  alkaline  with  ammonia  :  the 
characteristic  blue  coloration  of  copper  in  ammoniacal  solution  is  observed. 
The  liquid  is  then  acidified  with  hydrochloric  acid,  treated  with  hydrogen 


FIG.  28.     German  sheet 


FIG.  30.     Belgian  sheet 


FIG.  32.     Sheet  oxidised  with 
reagents 


FIG.  29.     English  sheet 


FIG.  31.     Belgian  sheet  (at  bend 


FIG.  33.     Sheet  oxidised  with  re- 
agents (at  bend) 


[To  face  p.  295. 


OXIDISING  295 

sulphide,  filtered,  boiled  to  expel  excess  of  hydrogen  sulphide,  made  alkaline 
with  ammonia,  heated  and  filtered.  In  the  nitrate,  acidified  with  acetic 
acid,  the  zinc  is  tested  for  with  potassium  ferrocyanide. 


OXIDISING 

For  increased  protection  against  atmospheric  agencies  or  for  the  sake 
of  appearance,  many  objects  are  coated  either  chemically  or  mechanically 
with  a  thin  layer  of  oxide,  which  imparts  to  them  a  brown  or  bluish-brown 
coloration. 

Similar  coloration  may,  however,  arise  spontaneously  during  the  working 
of  the  objects  owing  to  reheating  and  it  is  not  always  easy  to  decide  if  the 
oxidation  is  artificial  or  spontaneous.  One  distinguishing  character  is  the 
regularity  and  uniformity  of  the  layer  of  oxide  with  artificially  oxidised 
objects,  in  comparison  with  the  irregularity  of  layers  of  oxide  formed  spon- 
taneously ;  the  following  tests  are  based  on  this  criterion. 

1.  For  Copper  and   Brass   Objects. — The  surface  of  the  object  is 
thoroughly  freed  from  grease  by  means  of  benzene  and  treated  with  a  drop 
of  5%  mercuric  chloride  solution.     If  the  layer  of  oxide  is  very  regular 
and  compact,  the  reagent  will  not  get  into  contact  with  the  metal  and  no 
reaction  will  be  observed.     If,  however,  the  oxidation  is  irregular,  the  mer- 
curic chloride  undergoes  reduction  at  the  surface  of  the  metal,  forming  a 
grey  spot. 

2.  For  Objects  of  Iron. — After  being  cleaned  with  benzene,  the  oxidised 
surface  is  moistened  with  a  drop  of  5-6%  copper  sulphate  solution.     If 
the  oxidation  is  irregular  and  hence  not  artificially  formed,  a  spot  of  metallic 
copper  appears  either  immediately  or  after  some  time,  whereas,  if  the  oxida- 
tion is  regular  and  uniform,  any  reduction  which  may  occur  will  be  observable 
only  after  the  lapse  of  a  long  period. 

With  reference  to  this  test  it  is,  however,  to  be  noted  that  sheet  metal 
(lamiere  bleu-lisse)  is  now  put  on  the  market  covered  with  a  regular  layer 
of  ferroso-ferric  oxide  of  a  bluish  colour,  which,  although  obtained  during 
the  process  of  rolling  is  very  regular  and  uniform  and  does  not  allow  of  any 
reduction  of  copper  sulphate. 

Such  sheet  is  nevertheless  readily  distinguishable  from  that  oxidised 
by  means  of  reagents  or  the  like. 

1.  Technical  test.     When  a  sheet  of  this  character  is  bent  at  right  angles 
it  sheds  its  oxide  at  the  bend  in  the  form  of  scale  and  shows  the  naked  metal, 
whereas  sheet  oxidised  by  reagents  exhibits  little  change. 

2.  Microscopic  test.     Further,  microscopic  examination,  in  reflected  light 
and  under  a  magnification  of  100-120  diameters,  of  the  surface  of  such  sheet 
reveals  numerous  minute  fissures  which  have  been  made  in  the  oxide  during 
rolling  and  lie  parallel  to  the  axis  of  the  rolls.     Figures  28,  29  and  30  (see 
plate)  represent  reproductions  of  microphotographs  of  the  surfaces  of  three 
types  of  such  sheets  from  Germany,  England  and  Belgium,  while  Fig.  31 
shows  the  appearance  of  a  Belgian  sheet  at  the  bend. 

Metal  which  has  been  oxidised  with  reagents  exhibits  no  such  parallel 


296  OXIDISING 

• 

cracks,  but  numerous  small  rounded  pittings  produced  by  the  corrosive 
action  of  the  reagent  used  to  obtain  the  oxidation.  Fig.  32  is  a  reproduction 
of  the  microphotograph  of  the  surface  of  a  sheet  oxidised  with  reagents 
and  Fig.  33  that  of  the  surface  of  the  same  sheet  near  a  bend  ;  the  different 
behaviour  in  this  case  is  obvious. 


CHAPTER  VI 
FUELS 

Leaving  aside  wood,  which  is  rarely  examined  as  to  its  value  as  a  com- 
bustible, the  fuels  used  industrially  are  mainly  coal,  charcoal  and  mineral 
oils  ;  the  last  will  be  considered  later.  The  coals  are  distinguished  according 
to  the  degree  of  carbonisation  as  peat,  lignite,  bituminous  coal  and  anthracite. 
Extensive  use  as  a  fuel  is  also  made  of  coke,  the  residue  of  the  dry  distillation 
of  bituminous  coal,  the  volatile  products  being  illuminating  gas,  ammonia 
and  tar.  Fuel-blocks  (briquettes)  are  also  largely  used  at  the  present  time  ; 
these  are  obtained  by  the  compression  in  moulds  of  fragments  of  different 
coals,  usually  with  the  addition  of  cementing  materials.  In  this  way  waste 
coal  may  be  utilised  and  coal  which  is  inconvenient  to  use  on  account  of 
its  physical  condition  rendered  more  useful. 

The  quality  and  technical  value  of  coal  are  determined  by  chemical 
analysis  and  calorific  examination.  The  methods  adopted  are  the  same 
for  all  coals  and  are  described  below  under  the  heading  :  General  Methods. 
In  the  special  part  data  will  then  be  given  relating  to  each  of  the  different 
types  of  coal. 

In  all  cases,  selection  of  the  sample  is  of  great  importance. 

Sampling. — Coal  is  usually  far  from  homogeneous,  and  care  must  be 
taken  that  the  sample  for  analysis  represents  as  closely  as  possible  the  mean 
composition  of  the  whole  of  the  parcel  to  be  examined.  When  the  sample 
is  to  be  taken  from  a  mine  or  from  a  large  quantity,  portions  are  taken  with 
a  shovel  from  different,  regularly  distributed  points  of  the  mass,  a  large 
quantity  being  thus  collected.  The  larger  lumps  of  this  are  broken  up  and 
the  whole  well  mixed  and  spread  out  in  the  form  of  a  square  and  the  diagonals 
of  the  latter  drawn.  Two  opposite  triangles  are  then  discarded  and  the 
remaining  two,  further  disintegrated  and  mixed,  formed  into  another  square. 
These  operations  are  repeated  several  times  until  a  sample  of  about  2  kilos 
is  obtained,  this  being  reduced  to  small  pieces  and  stored  in  dry,  tightly 
closed  vessels.  When,  however,  the  laboratory  is  supplied  with  a  limited 
sample,  the  whole  of  the  latter  is  broken  up  and  stored  as  above. 

In  either  case,  a  portion  of  the  sample  thus  prepared  sufficient  for  the 
determinations  to  be  made  (about  200  grams)  is  reduced  to  coarse  powder 
and  store4  separately  in  a  dry,  air-tight  vessel.  Fo.  each  single  determina 
tion,  part  of  this  sample  is  powdered  to  the  degree  of  fineness  requisite  in 
each  case,  care  being  taken  not  to  throw  away  any  part.  Consequently, 
when  the  portion  taken  has  been  powdered  and  sieved  through  the  sieve 

297 


298  FUELS   (GENERAL  METHODS) 

of  the  proper  mesh,  that  remaining  on  the  sieve  must  be  again  powdered 
and  sieved  until  the  whole  has  passed  through. 


GENERAL   METHODS 
1.  Chemical  Analysis 

This  usually  includes  determinations  of  the  moisture,  ash,  coke  and 
volatile  substances,  and  sulphur  (see  i,  2,  3  and  4).  Of  interest  in  some 
cases  are  determinations  of  the  phosphorus,  carbon  and  hydrogen,  nitrogen 
and  oxygen  (see  5,  6,  7  and  8). 

1.  Determination  of  the  Moisture. — About  5  grams  of  the  substance, 
not  too  finely  powdered  (say,  to  pass  through  a  sieve  of  250  meshes  per 
sq.  cm.),  are  dried  in  an  oven  at  105-110°  to  constant  weight,  the  sample 
being  placed  in  a  covered  platinum  dish  or  crucible  or  between  two  watch- 
glasses  ;  as  a  rule  the  drying  does  not  require  more  than  two  hours.     Since 
dry  coal  dust,  especially  that  of  highly  bituminous  coal  and  lignites,  tends 
to  oxidise  in  the  air,  any  increase  in  weight  should  be  neglected  and  the 
preceding  weight  taken  as  constant.     In  such  cases,  when  highly  exact 
determinations  are  required,  the  drying  should  be  carried  out  in  a  boat 
in  a  current  of  carbon  dioxide. 

With  washed  coal,  peat  and  certain  earthy  lignites,  the  determination 
of  the  hygroscopic  moisture  is  preceded  by  that  of  the  water  oj  imbibition. 
For  this  purpose,  a  large  quantity  (at  least  i  kilo)  of  the  coal,  coarsely 
ground  and  weighed,  is  left  to  dry  in  the  air,  the  diminution  in  weight  repre- 
senting the  water  of  imbibition.  The  substance  thus  obtained  is  powdered 
and  used  for  determining  the  hygroscopic  moisture  and  other  constituents. 

2.  Determination  of  the  Ash. — From  2  to  5  grams  of  substance  (that 
used  for  the  determination  of  moisture  will  serve)  are  incinerated  either 
in  a  platinum  dish  in  a  muffle  or  in  an  open,  inclined  platinum  crucible 
resting  on  a  perforated  asbestos  card  over  a  bunsen  flame,  care  being  taken 
to  heat  gently  at  first  to  drive  off  the  volatile  substances  and  to  increase 
the  temperature  gradually  to  redness. 

In  some  cases  the  ash  is  analysed  chemically  to  determine  its  principal 
components  and  its  alkalinity ;  it  may  also  be  examined  from  the  point 
of  view  of  its  fusibility. 

3.  Determination    of    the    Coke    and     Volatile    Substances. — i 
gram  of  the  substance  (coals  rich  in  volatile  matters  are  best  coarsely  pow- 
dered, say  to  pass   through  a  sieve  of  100  meshes  per  sq.  cm.)  is  weighed 
in  a  platinum  crucible  30-35  mm.  high,  which  is  placed  covered  on  a  triangle 
of  platinum  wire  arranged  so  that  the  bottom  of  the  crucible  is  3  cm.  above 
the  apex  of  a  bunsen  burner  giving  a  flame  18-20  cm.  high.     When  the 
burner  is  lighted,  it  is  placed  at  once  under  the  crucible  and  maintained 
as  long  as  luminous  flames  issue  from  the  edges  of  the  crucible  ;    when 
these  cease — usually  after  not  more  than  two  minutes — the  flamp  is  extin- 
guished and  the  crucible,  without  opening  it,  placed  in  a  desiccator,  allowed 
to  cool,  and  weighed.     The  residue  in  the  crucible,  less  the  ash,  is  regarded 
as  coke  (fixed  carbon),  and  the  loss  in  weight,  less  the  moisture,  as  the 


FUELS   (GENERAL  METHODS)  299 

volatile  matter  (hydrocarbons  and  other  organic  substances).  The  appear- 
ance of  the  coke  is  noted  :  whether  it  is  pulverulent,  or  composed  of  frag- 
ments more  or  less  cemented  together,  or  fused,  and  in  the  last  case,  if  it 
is  compact  or  porous,  and  more  or  less  swollen. 

4  Determination  of  the  Sulphur. — The  sulphur  contained  in  fuels 
is  present  partly  as  sulphides  (pyrites)  and  sulphates,  and  partly Jn^orgamc 
compounds.  In  the  combustion  part  of  the  sulphur  (that  of  the  sulphates 
and  some  of  that  of  the  sulphides)  remains  in  the  ash,  whilst  the  remainder 
(the  organic  sulphur  and  part  of  that  of  the  sulphides)  passes  over  among 
the  products  of  combustion  (combustible,  injurious  or  volatile  sulphur) 
as  sulphur  dioxide  and,  in  small  proportion,  sulphur  trioxide. 

The  total  sulphur  is  determined  by  a  slight  modification  of  Eschka's 
method,  which  is  carried  out  as  follows :  About  i  gram  of  the  finely 
powdered  coal  (passing  a  sieve  of  650  meshes  per  sq.  cm.)  is^thoroughly 
mixed  in  a  roomy  platinum  crucible  with  about  1-5  gram  of  a  mixture  of 
magnesium  oxide  (2  parts)  and  dry  sodium-potassium  carbonate  (i  part) 
by  means  of  a  platinum  wire,  about  0-5  gram  of  the  same  mixture  being 
then  placed  on  the  top.  The  open  and  inclined  crucible  is  then  arranged 
in  the  hole  in  a  piece  of  asbestos  board  and  heated  over  a  small  flame  so 
that  only  its  lower  portion  is  reddened.  The  heating  is  continued  for 
about  an  hour — the  mixture  being  frequently  stirred  with  a  platinum  wire 
— until  the  grey  colour  has  changed  uniformly  to  yellowish,  reddish  or 
brown.  The  crucible  is  then  allowed  to  cool  and  the  contents  washed  with 
hot  water  into  a  beaker  and  the  liquid  made  feebly  yellow  with  a  little 
bromine  water,  boiled,  and  filtered,  the  residue  being  washed  with  boiling 
water.  The  filtrate  is  acidified  with  hydrochloric  acid,  boiled  to  expel 
the  remaining  free  bromine,  and  the  colourless  liquid  precipitated  with 
barium  chloride  and  the  barium  sulphate  weighed  as  usual. 

If  the  fixed  and  volatile  sulphur  are  required  separately,  the  former  is 
determined  directly.  To  this  end,  a  weighed  quantity  of  the  coal  sufficient 
to  give  i—2  grams  of  ash  is  incinerated  and  the  ash  treated  in  the  hot  in  a 
porcelain  dish  with  hydrochloric  acid  and  a  little  potassium  chlorate  or 
bromine  to  oxidise  any  sulphites  formed  as  well  as  the  sulphides.  The 
excess  of  chlorine  or  bromine  is  expelled  by  boiling,  the  liquid  precipitated 
with  ammonia  and  filtered,  and  the  filtrate  acidified  and  precipitated  with 
barium  chloride  in  the  usual  way :  BaS04  x  0-1374  =  S.  Total  sulphur 
minus  fixed  sulphur  =  volatile  sulphur. 

5.  Determination  of  the  Phosphorus. — This  is  carried  out  on  the 
ash  (i— 2  grams),  which  is  digested  with  cone,  hydrochloric  acid  in  a  porcelain 
dish  on  a  water-bath,  evaporated  to  dryness  and  the  residue  moistened  with 
hydrochloric  acid,  diluted  with  water,  filtered  into  another  porcelain  dish 
and  taken  almost  to  dryness  with  several  additions  of  nitric  acid.     The 
residue  is  then  taken  up  in  water  acidified  with  nitric  acid  and  precipitated 
in  a  beaker  with  ammonium  molybdate  and  so  on  (see  Determination  of 
Phosphorus  in  Iron,  p.  173). 

6.  Determination  of  the  Carbon  and  Hydrogen. — These  are  deter- 
mined by  the  ordinary  method  followed  for  the  elementary  analysis  of 
organic  substances,  the  substance  being  burnt  in  a  current  of  oxygen  and 


300  FUELS    (GENERAL  METHODS) 

in  presence  of  copper  oxide  and  lead  chromate,  copper  spirals  also  being 
used.  About  0-4  gram  of  substance,  not  too  finely  powdered,  is  used.  At 
the  beginning  of  the  combustion,  it  is  well  to  heat  moderately  and  in  a 
current  of  air  rather  than  of  oxygen  ;  when  the  volatile  products  are  burnt 
— this  being  easily  judged  from  the  aspect  of  the  coke  remaining  in  the 
boat — the  fixed  carbon  is  burnt  at  a  high  temperature  in  a  current  of  oxygen. 
If  the  undried  substance  is  employed,  the  moisture  content  must  be  allowed 
for. 

7.  Determination  of  the  Nitrogen. — This  is  made  on  075—1  gram 
of  the  finely  powdered  sample  by  Kjeldahl's  method  (see  Fertilisers,  p.  123). 

8.  Determination  of  the  Oxygen. — This  is  calculated  by  difference, 
the  percentages  of  carbon,  hydrogen,  nitrogen,  volatile  sulphur,  ash  and 
moisture  being  added  and  the  sum  subtracted  from  100. 


2.  Determination  of  the  Calorific  Power 

The  calorific  power  of  a  fuel,  is  the  quantity  of  heat  generated  by  the 
complete  combustion  of  i  gram  of  the  fuel,  expressed  in  small  calories. 

The  small  calorie  (cal.)  is  the  amount  of  heat  necessary  to  raise  by  i°C.  (more 
exactly  from  o°  to  i°)  the  temperature  of  i  gram  of  water.  Some  refer  the 
calorific  power  to  i  kilo  and  use  as  unit  of  heat  the  large  calorie  (cal.),  which  is 
the  amount  of  heat  required  to  raise  by  i°  C.  the  temperature  of  i  kilo  of 
water  ;  the  numbers  are  the  same  in  the  two  cases. 

In  some  cases  also  the  evaporative  power  of  a  fuel  is  calculated,  this  repre- 
senting the  number  of  kilos  of  water  at  o°  which  could  be  transformed  into 
aqueous  vapour  at  100°  by  the  combustion  of  i  kilo  of  the  fuel.  Since  each 
kilo  of  water  requires  637  large  calories  (100  to  bring  it  from  o°  to  100°  and 
537  to  transform  it  into  steam  also  at  100°),  the  evaporative  power  is  obtained 
by  dividing  the  calorific  power  by  637. 

The  calorific  power  of  a  fuel  may  be  calculated  approximately  from 
the  chemical  composition,  but  it  is  best  to  determine  it  directly  by  calori- 
metric  methods.  The  calorific  value  is  referred,  according  to  circumstances, 
to  the  fuel  as  such  or  simply  dried,  or  to  the  pure  fuel  (moisture  and  ash 
being  deducted). 

1.  Calculated  Calorific  Power. — Formulae  derived  from  that  of 
Dulong  are  used,  but  the  results  are  only  moderately  satisfactory.  Accord- 
ing to  Mahler, l  that  to  be  preferred  is  the  following,  which  gives,  with  most 
coals,  errors  not  exceeding  3%  : 

p  =  81400  +  345ooH  —3000(0  +  N), 

where  C,  H,  O  and  N  are  the  respective  quantities  of  carbon,  hydrogen, 
oxygen  and  nitrogen  contained  in  i  gram  of  the  pure  fuel  (moisture  and 
ash  deducted)  and  p  is  the  required  calorific  value,  referred  to  the  pure  fuel. 
By  putting 

0+N=i-C—  H, 

the  above  formula  simplifies  to  : 

p  =  111406  +  375ooH  —3000. 

1  Etudes  sur  les  combustibles  solides,  liquides  et  gazeux  (Paris,  IQ°3).  PP-  4  and  56- 


FUELS  (GENERAL  METHODS) 


301 


A  totally  different  formula  which  permits  of  the  calculation  of  the 
calorific  value  of  coals  with  a  high  degree  of  approximation  is  that  proposed 
by  Goutal,1  namely  : 

p  =  82C  +  aV, 

where  p  is  the  calorific  power  of  the  fuel  as  such,  C  and  V  are  the  percentages 
of  fixed  carbon  (coke  less  ash)  and  volatile  matter  (less  moisture)  and  a  a 
coefficient  expressing  the  calorific  power  (divided  by  100)  of  the  volatile 
matters  and  varying  with  the  amount  of  these  volatile  matters.  To  deter- 
mine the  value  to  be  ascribed  to  a  the  percentage  V1  of  volatile  matters 
in  the  fuel  supposed  free  from  moisture  and  ash  is  calculated  by  the  formula, 

V1  =        —  ;    the  corresponding  value  of  a  is  then  obtained  from  the 
C  + V 

following  table  : 


V1 

a 

V1 

a 

V1 

a 

V1 

a 

Less  than  5 

IOO 

14 

I2O 

23 

I°5 

32 

97 

5 

145 

15 

117 

24 

104 

33 

96 

6 

142 

16 

H5 

25 

103 

34 

95 

7 

139 

17 

H3 

26 

IO2 

35 

94 

8 

136 

18 

112 

27 

IOI 

36 

91 

9 

133 

19 

no 

28 

IOO 

37 

88 

10 

130 

20 

IO9 

29 

99 

38 

85 

ii 

127 

21 

108 

30 

98 

39 

82 

12 

124 

22 

107 

31 

97 

40 

80 

13 

122 

2.  Calorimetric    Determination    of    the    Calorific    Power. — The 

calorimetric  or  direct  methods  are  undoubtedly  to  be  preferred  to  those 
just  mentioned  as  they  give  far  more  certain  results. 

The  numerous  forms  of  apparatus  devised  for  such  determinations  may 
be  grouped  in  three  classes  :  (i)  calorimeters  in  which  the  combustion  takes 
place  in  a  stream  of  air  or  oxygen  at  the  ordinary  pressure,  like  those  of 
Favre  and  Silbermann,  Alexejew,  Schwackhofer,  and  F.  Fischer;  (2) 
calorimeters  in  which  the  combustion  occurs  with  the  aid  of  an  oxidising 
substance  mixed  with  the  fuel,  as  in  those  of  Lewis  Thompson,  Stohmann, 
and  Parr  ;  (3)  calorimeters  in  which  the  combustion  is  effected  with  oxygen 
at  constant  volume  and  very  high  pressures,  known  as  calorimetric  bombs  ; 
the  first  such  bomb  was  due  to  Berthelot  and  Vieille  and  on  this  were  based 
the  more  practical  and  cheaper  ones  of  Mahler,  Hempel  and  Kroeker,  which 
are  the  most  suitable  forms  of  apparatus  for  exact  determinations. 

Only  the  types  most  commonly  used  will  be  described  here. 

(a)  LEWIS  THOMPSON  CALORIMETER.  This  is  a  very  simple  apparatus 
giving  only  approximate  results  comparable  among  themselves  ;  it  is, 
however,  still  in  common  use  in  England,  where  contracts  are  made  on  the 
basis  of  its  indications.  It  consists  (Fig.  34)  of  a  large  glass  cylinder  with 


1  Comptes  Rendus  de  I'Acad.  des  Sciences,  1902,   CXXXV,  pp.  477-479. 


302 


FUELS   (GENERAL  METHODS) 


a  mark  at  two  litres,  and  a  brass  foot  fitted  with  a  small  cylindrical  copper 
capsule  or  furnace  in  which  the  combustion  occurs.  The  capsule  is  covered 
with  a  copper  cylinder  with  a  row  of  holes  round  the  bottom  and  a  tube 
with  a  tap  at  the  top  ;  this  cylinder  is  held  in  place  by  four  springs  on  the 
brass  foot.  A  thermometer  reading  to  0-1°,  and  protected  by  a  metal  guard, 
is  also  required. 

2  grams  of  the  fuel,  ground  in  an  iron  mortar  to  pass  through  a  No.  6 
sieve  (650  meshes  per  sq.  cm.),  are  thoroughly  mixed  on  a  piece  of  shining 
paper  by  means  of  a  flexible  steel  spatula  with  the  oxidising  mixture  (3 
parts  of  powdered,  dry  potassium  chlorate  and  i  part  of  potassium  nitrate, 
carefully  mixed  without  using  the  iron  mortar  and  passed  through  a  No.  6 
sieve),  sufficient  of  the  latter  being  used  to  give  a  homogeneous,  lead-grey 
mixture,  which  should  burn  completely,  regularly  and  moderately  rapidly. 
The  amount  of  oxidising  mixture  necessary  is  usually  20—30  grams  per  2 
grams  of  fuel,  but  it  varies  with  the  character  of  the  fuel  and  should  be 

determined  by  preliminary  trial. 

By  means  of  the  spatula  used  before,  the 
mixture  is  placed  in  the  coppei  capsule  in 
such  a  way  as  to  compress  it  uniformly  and 
as  little  as  possible  ;  if  the  quantity  of  the 
mixture  is  too  great  to  be  held  by  the  capsule 
without  compression,  it  is  advisable  to  use 
only  i  gram  of  the  fuel  and  the  corresponding 
amount  of  the  oxidising  mixture.  On  the 
top  of  the  mixture  is  placed  a  piece  of  slow 
match,1  which  should  protrude  about  a 
centimetre,  the  copper  cylinder  fitted,  the 
tap  closed  and  the  whole  immersed  in  the 
water  in  the  glass  cylinder ;  the  water 
should  be,  according  to  circumstances,  be- 
tween 2°  and  7°  lower  than  the  temperature 
of  the  air.2  The  water  is  mixed  by  means  of  the  apparatus  itself  and  the  tem- 
perature shown  on  the  thermometer  noted  ;  the  apparatus  is  then  with- 
drawn, the  match  lighted,  the  cover  rapidly  replaced  and  the  whole  at 
once  placed  in  the  water  before  the  mixture  ignites.  After  a  few  seconds, 
when  ignition  occurs,  the  gaseous  products  issue  turbulently  from  the  holes 
in  the  cover  and  escape  upward  through  the  water. 

At  the  end  of  the  combustion,  which,  if  regular,  requires  one  or  two 
minutes,  the  tap  is  opened,  the  tube  unstopped  by  means  of  an  iron  wire 
and  the  water  stirred  with  the  apparatus,  the  highest  temperature  reached 
being  observed.  The  rise  of  temperature,  increased  by  one-tenth  to  correct 
approximately  for  the  losses  and  for  the  heat  absorbed  by  the  apparatus, 
is  multiplied  by  the  weight  of  water  in  the  glass  cylinder.  The  product 

1  Made  from  cotton  lighting  wick  (or  better  of  de-fatted  jute)  immersed  in  con- 
centrated potassium  nitrate  solution  and  dried  in  an  oven. 

2  For  ordinary  air  temperatures,  the  temperature  of  the  water  should  be  as  follows  : 

Air  temperature  .          .     10°          15°  20°  25°  30° 

Water  temperature       .          .     7-9°         11-9°         15-9°         197°         23-2° 


FIG.  34 


FUELS   (GENERAL  METHODS)  303 

represents  the  heat  generated  by  the  combustion  of  the  fuel,  and  this, 
divided  by  the  weight  of  the  fuel,  gives  the  calorific  power  sought. 

The  capsule  should  be  examined  to  ascertain  if  any  appreciable  quantity 
of  the  coal  remains  unburnt.  It  is  advisable  to  make  several  tests  on  each 
sample,  the  highest  result  obtained,  and  not  the  mean,  being  regarded  as 
correct.  It  should  be  pointed  out  that,  under  the  above  conditions,  coke 
and  anthracite  burn  with  difficulty,  while  peat  and  many  bituminous  lignites 
burn  only  incompletely. 

In  some  Thompson  calorimeters  of  English  construction,  the  amount  of 
water  placed  in  the  glass  cylinder  weighs  29,010  grains  (1879-85  grams).  When 
30  grains  (1-944  grams)  of  the  fuel  are  burnt,  since  29010  -f-  30  =  967  =  537 
X  9  -r  5,  the  rise  in  temperature  in  Fahrenheit  degrees  (increased  by  one- 
tenth)  indicates  directly  the  grains  of  water  at  100°  transformable  into  steam 
at  100°  by  the  heat  generated  by  one  grain  of  the  fuel,  i.e.,  the  evaporative 
power  calculated  for  water  at  100°  and  not,  as  usual,  at  o°. 

It  may  be  pointed  out  that,  in  England,  calorific  powers  are  mostly  expressed 
in  terms  of  the  British  Thermal  Unit  (B.T.U.),  which  is  the  quantity  of  heat 
necessary  to  raise  the  temperature  of  i  Ib.  of  water  (0-4536  kilo)  by  i°  Fahrenheit. 
The  large  calorie  =  3-9683  B.T.U.  and  i  B.T.U.  =  0-252  large  calorie.  Further, 
a  calorific  power  of  x  calories  per  kilo  corresponds  with  1-8  x  B.T.U.  per  pound, 
or  x  B.T.U.  per  pound  is  equivalent  to  0-5555  x  calories  per  kilo. 

With  other  Thompson  calorimeters,  the  glass  cylinder  is  marked  at  2000 
c.c.  and  also  at  2148  c.c.  (=  537  X  4).  If  the  latter  quantity  of  water  is  taken 
and  2  grams  of  the  fuel  are  used,  the  rise  of  temperature  (increased  by  one-tenth), 
multiplied  by  2,  will  give  directly  the  evaporative  power  (referred  to  water  at 
1 00°  C.  and  therefore  not  to  the  standard  usually  adopted  :  see  later). 

(6)  MAHLER  BOMB  CALORIMETER.  This  apparatus  (Fig.  35),  which  is 
among  the  best  of  those  employed,  consists  of  a  vessel  or  bomb  a  of  fairly 
pure,  forged  mild  steel,  nickelled  outside  and  enamelled  inside  :  capacity 
about  650  c.c.,  thickness  of  walls  8  mm.,  weight  about  4  kilos.  The  bomb 
is  closed  by  a  screwed  iron  lid  b  with  lead  packing  and  furnished  in  the 
centre  with  a  ferro-nickel  conical  screw  valve  r.  The  cover  supports  the 
terminals,  consisting  of  two  platinum  rods  e,  one  passing  through  the  cover 
and  insulated  from  it  and  the  other  fixed  directly  to  the  cover  and  supporting 
a  flat  platinum  dish  c  in  which  the  fuel  is  placed.  The  two  terminals  are 
connected  by  a  small  spiral  of  very  thin  iron  wire  which  burns  on  passage 
of  the  current  (about  2  amps,  at  8— 10  volts)  and  so  ignites  the  fuel  in  contact 
with  it. 

The  bomb  rests  on  supports  on  the  bottom  of  the  brass  calorimetric 
vessel  A,  which  contains  2,200  grams  of  water,  a  thermometer  t  divided 
into  fiftieths  of  a  degree  and  allowing  0-01°  to  be  estimated,  and  a  spiral 
stirrer  d.  To  protect  it  from  external  influences,  the  calorimeter  is  placed 
inside  a  double-walled  metallic  vessel  B  filled  with  water  and  covered  with 
felt. 

To  make  a  determination,  exactly  i  gram  of  the  fuel,  not  too  finely 
powdered,  is  weighed  into  the  capsule  c  and  this  placed  in  the  bomb  after 
one  of  the  iron  wire  spirals  has  been  fitted  to  the  terminals  so  that  it  conies 
into  contact  with  the  fuel.  The  lid  b  is  screwed  tightly  down,  the  valve 
connected  with  a  cylinder  of  compressed  oxygen  by  means  of  a  copper 


FUELS  (GENERAL  METHODS) 


tube  carrying  a  manometer  and  the  bomb  slowly  filled  with  oxygen  1  until 
the  pressure  is  20—25  atmos.  (or  less,  if  the  coal  burns  very  easily).  The 
bomb  is  then  placed  in  the  calorimeter  A,  into  which  the  proper  amount 
of  water  is  poured,  the  thermometer  t  being  placed  in  position,  the 
stirrer  d  started  and  the  temperature  read  off  every  minute.  After  five 
minutes,  ignition  is  caused  by  the  momentary  passage  of  the  current.  The 
temperature  is  read  half  a  minute  after  ignition,  after  a  further  half-minute, 
and  then  each  minute  until  the  maximum  temperature  is  reached  (after 
3  or  4  minutes)  and  for  five  minutes  during  the  subsequent  fall  in  tem- 
perature. 

At  the  end  of  the  experiment,  the  tap  r  of  the  bomb  is  opened  to  allow 
the  gas  to  escape,  the  bomb  itself  being  then  opened  and  washed  out  inside 
*  with    a    little    distilled     water.2 

The  nitric  acid  formed  from  the 
nitrogen  contained  in  the  bomb 
is  determined  in  the  wash  water 
by  titration  with  caustic  potash 
solution  (i  c.c.  =  o-oi  gram 
HN03)  in  presence  of  methyl 
orange.  Any  sulphuric  acid 
formed  is  also  calculated  as 
nitric  acid,  but  with  fuels  poor 
in  sulphur  no  appreciable  error  is 
introduced  in  this  way.  When, 
however,  allowance  is  to  be  made 
for  the  sulphuric  acid,  the  proce- 
dure is  as  follows :  The  wash 
water  is  heated  for  a  short  time 
to  expel  carbon  dioxide  and 
titrated  with  N/io- baryta  in 
presence  of  phenolphthalein  ; 
excess  of  standard  sodium  car- 

T-.  bonate  solution  is  then  added  and 

"  IG.  35 

the    excess  titrated    with    N/io- 

hydrochloric  acid  in  presence  of  methyl  orange.  The  volume  of  baryta 
solution  used  corresponds  with  the  sulphuric  and  nitric  acids  together, 
and  that  of  the  sodium  carbonate  solution  with  the  nitric  acid  alone. 

In  calculating  the  results  of  the  measurement,  it  is  first  necessary  to 
establish  the  correction  necessary  owing  to  the  exchange  of  heat  with  the 
surrounding  air  in  the  interval  of  time  between  ignition  and  the  attainment 

1  Compressed  oxygen,  if  obtained  electrolytically,  often  contains  hydrogen,  which 
appreciably  alters  the  results  of  the  calorimetric  experiments.     In  such  case  it  is  neces- 
sary to  purify  it,  before  admitting  it  to  the  bomb,  by  passing  it  slowly  through  a  red- 
hot  copper  tube  and  then  through  a  coil  cooled  with  water.     On  the  other  hand,  oxygen 
from  liquid  air,  containing  appreciable  quantities  of  nitrogen,  has  the  disadvantage 
of  giving  rise  to  the  formation  of  nitric  acid,  allowance  for  which  must  be  made  in 
calculating  the  results. 

2  With  fuels  poor  in  hydrogen  and  hence  yielding  little  water  when  they  burn,  a 
few  c.c.  of  water  may  be  placed  in  the  bottom  of  the  bomb  before  closing  it  so  that 
the  products  of  oxidation  of  the  nitrogen  and  sulphur  may  be  dissolved. 


FUELS   (GENERAL  METHODS)  305 

of  the  maximal  temperature.  This  correction  is  easily  made  by  means  of 
the  thermometer  readings  before  ignition  and  after  the  maximum,  these 
giving  the  mean  thermometric  variations  per  minute  in  the  preliminary 
and  final  periods.  It  is  then  assumed  that,  during  every  minute  of  the 
period  between  ignition  and  the  attainment  of  the  maximum  temperature 
the  temperature  varies  uniformly,  so  that  the  correction  may  be  referred 
to  the  mean  temperature  of  the  minute  considered.  If  the  mean  tempera- 
ture of  a  definite  minute  differs  by  less  than  1°  from  the  maximum,  it  is 
held  that  the  diminution  of  temperature  due  to  loss  of  heat  during  that 
minute  is  equal  to  the  mean  diminution  in  every  minute  after  the  maximal 
temperature  *  if,  however,  the  mean  temperature  of  any  minute  differs 
from  the  maximum  by  more  than  i°  and  less  than  2°,  the  correction  for 
that  minute  is  taken  as  the  mean  diminution  after  the  maximum  tempera- 
ture, decreased  by  0-005°.  Finally,  for  the  first  half-minute  after  ignition 
it  is  assumed  that  the  variation  is  equal  to  the  mean  observed  before  the 
ignition. 

Besides  this  correction,  account  must  also  be  taken  of  (i)  the  heat  of 
combustion  of  the  iron  coil,  1-6  cal.  being  allowed  per  milligram  of  iron,  and 
(2)  the  heat  of  formation  of  the  nitric  acid,  which  is  0-23  cal.  per  milligram 
of  nitric  acid  (also  of  the  heat  of  formation  of  sulphuric  acid  ;  in  the  open 
air,  sulphur  dioxide  will  be  formed  and  the  correction  to  be  subtracted  is 
2-25  cals.  per  milligram  of  sulphur  or  0-73  cal.  per  milligram  of  sulphuric 
acid). 

The  calorific  power  p  (in  the  case  where  the  sulphuric  acid  has  been 
calculated  as  nitric  acid)  is,  therefore,  expressed  by  the  following  formula  : 

p  =  (T1-  —  T  +  t}(A  +  a)  —  o-23M  — 1-6/  .  .  .  (i), 
where, 

T   =  observed  temperature  before  ignition, 

T1  =  maximum  temperature, 

t     =  correction  for  heat  given  up  to  surrounding  air, 

A^  =  weight  of  water  in  the  calorimeter, 

a     =  water-equivalent  of  the  apparatus,  this  being  determined  once  and 

for  all  in  a  preliminary  experiment,1 
n    =  milligrams  of  nitric  acid  formed, 
j      =  milligrams  of  iron  in  the  igniting  coil. 

As  regards  this  calculation,  it  may  be  pointed  out  that  the  various 
corrections  indicated  above  compensate  one  another  partly,  so  that,  for 

1  The  water-equivalent  is  the  weight  of  water  requiring  the  same  amount  of  heat 
to  raise  its  temperature  i°  as  the  calorimetric  apparatus  (vessel,  stirrer,  thermometer, 
etc.).  It  is  determined  by  an  experiment  with  a  substance  of  known  heat  of  com- 
bustion (e.g.,  naphthalene,  9692  ;  cane  sugar,  3957  ;  benzoic  acid,  6330  cals.). 
The  difference  between  the  true  calorific  power  of  the  substance  and  that  calculated 
from  the  experimental  results  without  taking  account  of  the  heat  absorbed  by  the 
apparatus,  divided  by  the  rise  of  temperature,  gives  the  required  water- equivalent, 
if  it  is  not  thought  desirable  to  allow  for  the  corrections  for  the  rigorously  exact  calcu- 
lation ;  otherwise,  a  is  deduced  from  equation  (i). 

The  water-equivalent  may  also  be  calculated  theoretically  (with  less  reliable  results) 
by  multiplying  the  weights  of  the  different  parts  of  the  apparatus  by  the  specific  heats 
of  the  materials  from  which  they  are  made  and  adding  together  the  products  thus 
obtained. 

A.C.  20 


306  FUELS   (GENERAL  METHODS) 

ordinary  practical  purposes,  sufficiently  exact  results  are  obtained  if  the 
corrections  are  omitted.  Under  such  circumstances  the  thermometric 
readings  during  the  preliminary  period  and  those  after  the  maximum  tem- 
perature has  been  passed,  and  also  the  titration,  becomes  useless,  the  only 
values  required  being  those  of  the  magnitudes  in  the  expression, 


«)  .....      (ii), 
which  then  gives  the  calorific  power. 

It  must  also  be  mentioned  that,  whilst  in  the  bomb  the  water  (hygroscopic 
water  plus  that  formed  by  combustion  of  the  hydrogen  in  the  fuel)  remains 
in  the  liquid  state,  in  practice  it  passes  off  as  vapour  among  the  products  of 
combustion  ;  consequently,  the  calorific  power  calculated  as  above  includes 
also  the  heat  of  condensation  of  the  water,  which  in  practice  is  not  utilisable. 
In  France  the  calorific  power  resulting  from  the  above  calculation,  that  is, 
presupposing  the  formation  of  liquid  water  (also  called  gross  calorific  power)  is 
given,  whereas  in  Germany,  Austria,  and  elsewhere,  the  heat  of  condensation 
of  the  water  is  deducted,  the  assumption  being  made  that  the  water  remains 
as  vapour  (net  calorific  power).  Taking  600  cals.  as  the  heat  of  condensation 
of  i  gram  of  aqueous  vapour,  if  H  and  M  are  the  percentages  of  hydrogen  and 
moisture  in  the  fuel,  the  deduction  to  be  made  from  the  gross  calorific  power 
to  obtain  the  net  value  is  6  (M  +  gH).  Where  an  elementary  analysis  is  not 
made,  a  separate  determination  may  be  made  of  the  total  water  evolved  during 
the  combustion  (by  burning  a  given  weight  of  fuel  in  a  tube  and  collecting  the 
water^in  an  absorption  apparatus),  or,  as  Mahler  suggests,  in  practical  cases 
mean  values  of  H  may  be  taken  according  to  the  quality  of  the  fuel  tested. 

EXAMPLE  :    The  experimental  data  obtained  were  as  follows  : 

A  =  2200  grams. 

a  =     474       „ 


18-250° 

18-305   (max.) 

18-290 

18-275 

18-260 

18-245 

18-230 

Hence  T1  —  T  =  18-305  —  15-205  =  3-100°.     The  law  of  variation  before 

ignition  is  given  by 

15-205  —  15-180 


n  =  0-125 

,, 

/    =  0-032 

,, 

Temperature  observed  : 

o  minutes 

15-180° 

7 

minutes 

i 

15-185 

8 

,, 

2             ,, 

15-190 

9 

,, 

3 

I5-I95 

10 

.1 

4 

15-200 

ii 

,, 

5 

15-205   (ignition) 

12 

.. 

5i       - 

I5-795 

13 

,, 

6 

17-850 

5 
and  that  after  the  maximum  is  passed  by 


0-005  , 


18-305  —  18-230 

£_  =  0-015°. 

5 

The  correction  to  be  made  for  the  first  half-minute  after  ignition  is  hence 

— — =  —0-0025°  I  for  the  next  half-minute  it  is —   =  0-005, 

2  2 

and  for  each  of  the  minutes,  6-7  and  7-8,  it  is  0-015.     Hence 
t  =  2  X  0-015  +  0-005  ~"  O<oo25  =  O'°325» 


FUELS  (GENERAL  METHODS) 


307 


Equation  (i)  then  gives 

p  =  (3-100  +  0-0325) (2200  +  474)  —  0-23  X  125  —  1-6X3-2  =  8296-4  cals 
Calculating  without  corrections  according  to  formula  (ii), 
p  =  3-1  X  (2200  +  474)  =  8289-4  cals. 

In  this  way  the  gross  calorific  power  is  found.  If  the  fuel  contains  3%  of 
moisture  and  4-5%  of  hydrogen,  6  (3  +  9  x  4-5)  =  261  cals.,  must  be  subtracted 
from  the  results  to  obtain  the  net  calorific  power,  which  is  therefore  8035-4 
(corrected)  or  8028-4  (uncorrected) . 

(c)  HEMPEL'S  CALORIMETRIC  BOMB.  This  apparatus,  which  is  simpler 
and  cheaper  than  that  of  Mahler,  consists  (Fig.  36)  of  a  cylindrical,  thick- 
walled,  cast-iron  autoclave  A,  holding 
about  250  c.c.  and  coated  inside  with 
a  thin  layer  of  enamel.  It  has  a  screw 
lid  B,  which  fits  air-tight  by  means  of 
an  annular  lead  washer  and  has  an 
aperture  closable  by  a  conical  screw 
valve  a.  The  lid  carries  two  rods, 
one,  b,  connected  directly  with  it,  and 
the  other,  c,  insulated  by  means  of  a 
rubber  coating  from  the  lid,  through 
which  it  passes.  Each  rod  terminates 
below  in  a  platinum  wire  bent  to  a 
hook  to  support  a  capsule  d  of  refrac- 
tory earth,  in  which  is  placed  the  fuel 
compressed  into  cylindrical  form  in  a 
mould.  Between  the  two  wires  is 
fitted  another  very  thin  platinum  wire, 
which  penetrates  into  the  cylinder  of 
fuel  and  ignites  the  latter  when  heated 
to  redness  by  a  current. 

The  calorimeter  is  a  cylindrical 
copper  vessel  G  containing,  besides  the 
bomb,  about  i  litre  of  water  and 
placed  in  a  wooden  vessel  H  so  that 
the  distance  between  the  walls  is  2  cm. 
The  whole  is  then  closed  by  a  cover, 
through  which  pass  the  two  terminals, 
a  thermometer  t  to  read  to  0-01°  and  a  stirrer  m. 

The  powdered  fuel  is  pressed  into  a  cylinder  weighing  about  i  gram 
into  which  the  igniting  wire  is  already  pressed.  It  is  weighed  exactly  and 
placed  in  the  dish  d  and  the  bomb  closed,  oxygen  being  then  passed  in  slowly 
until  the  pressure  becomes  about  15  atmos.  The  valve  a  is  then  closed 
and  the  bomb  placed  in  a  beaker  of  water  to  ascertain  if  it  is  air-tight  ; 
this  being  the  case,  it  is  dried  and  arranged  in  the  calorimeter,  the  stirrer 
being  put  in  motion  and  the  thermometer  read  at  intervals  of  a  minute. 
After  the  temperature  has  remained  constant  for  five  minutes,  the  current 
is  passed  momentarily  to  cause  ignition  and  the  stirring  continued  and  the 
periodic  reading  of  the  thermometer  continued  until  the  temperature  passes 


FIG.  36 


308  WOOD   CHARCOAL— PEAT 

its  maximum.  The  weight  of  water,  plus  the  water-equivalent  of  the 
calorimeter  (usually  determined  once  for  all  by  a  preliminary  measurement), 
multiplied  by  the  rise  of  temperature,  gives  the  heat  generated.  For  a 
more  exact  calculation,  the  corrections  indicated  for  the  Mahler  apparatus 
may  be  introduced. 

Kroeker  has  modified  the  Hempel  bomb  by  the  addition  to  the  lid  of 
a  second  valve  inserted  in  a  platinum  tube  leading  almost  to  the  bottom 
of  the  bomb  for  the  admittance,  after  the  combustion,  of  a  current  of  dry 
air  into  the  bomb  heated  at  105°  and  the  absorption  of  the  expelled  water 
vapour  in  a  weighed  calcium  chloride  solution.  The  amount  of  the  total 
water  thus  determined  is  used  in  calculating  the  net  calorific  power. 


SPECIAL  PART 
WOOD    CHARCOAL 

This  is  distinguished  as  hard  or  soft,  according  as  it  is  made  from  hard 
or  soft  wood,  and  as  red  or  black  according  to  the  degree  of  carbonisation 
to  which  it  has  been  subjected.  The  black,  composed  principally  of  carbon, 
is  in  the  more  common  use. 


* 
*  * 


Charcoal  contains  usually  80-90%  C,  1-3%   H,  2-4%  O,   6-10%  H,O  and 
J~3%  asn-     As  a  rule,  its  calorific  power  lies  between  6500  and  7500  cals. 


PEAT 

This  is  a  fuel  of  somewhat  diverse  origins  and  may,  therefore,  exhibit 
very  varied  aspect  and  composition.  According  to  its  origin,  it  is  distin- 
guished as  marsh,  heath,  meadow,  forest,  and  marine  peat,  and  according 
to  its  appearance  as  mucous,  spongy,  herbaceous,  earthy,  compact,  lignite- 
like,  etc. 

*** 

When  freshly  extracted,  peat  always  contains  a  considerable  quantity  of 
water,  which  may  vary  from  50  to  90%,  whilst,  when  air-dried,  it  still  contains 
IO-3°%  of  moisture.  The  percentage  of  ash  varies  widely  and  may  be  as  much 
as  20-30%  or  even  much  more. 

The  best  peats  have  compositions  lying  between  the  following  limits,  which 
refer  to  the  dry  product  : 

Carbon       ........  5o_6o% 

Hydrogen  .          .          .  ..      .....  5-7  % 

Oxygen      ....                                .  30-35% 

Nitrogen    ........  1-2% 


The  calorific  value  of  a  good  peat  usually  varies  between  3,000  and  4,000 
calories,  but  a  value  of  5,000  cals.  may  be  reached  with  dry  peats  poor  in  ash. 


LIGNITE— COAL  309 


LIGNITE 

This  exists  in  several  varieties.  Sometimes  it  has  the  aspect  and  colour 
of  wood  (fossil  wood]  and  sometimes  it  is  brown,  friable  and  easy  to  break 
(peaty,  earthy  lignite]  ;  in  some  cases  it  consists  of  superposed  layers  (schistose 
lignite]  and  in  others  is  compact  and  varying  in  colour  from  brown  to  shining 
black  (pitch >• coal]. 


When  newly  won,  lignites  contain  20-60%  of  moisture,  and  when  air-dried, 
10-20%.  The  percentage  of  ash  is  very  variable  and,  although  it  usually  varies 
-rom  2  to  15%,  it  may  also  be  much  greater.  The  elementary  composition 
referred  to  the  fuel  free  from  ash  and  moisture,  generally  varies  between  the 
following  limits  : 

Carbon 55~75% 

Hydrogen  ...                                                   .  4-7% 

Oxygen      .                               .....  20-35% 

Nitrogen 0-5-2% 

In  some  lignites  sulphur  may  be  present  in  marked  proportions.  The  calorific 
power  of  good  lignites  varies  from  4,000  to  6,500  cals. 

Table  XXXVII  (see  p.  310)  gives  the  analytical  results  for  various  lignites. 


GOAL 

Coal  proper  includes  the  bituminous  coals  and  anthracite  ;  there  is  a 
gradual  transition  from  the  one  to  the  other  and  no  sharp  delimitation. 
They  constitute  the  most  important  industrial  fuels.  They  are  usually 
compact  and  black,  the  following  types  being  distinguished  :  shining, 
black  coal ;  opaque,  black  ;  cannel,  of  a  velvety,  blackish  colour,  with  a 
conchoidal  fracture  ;  fibrous  coal ;  and  bituminous  slates  (boghead). 

*  * 

According  to  their  chemical  composition,  coals  are  classified,  after 
Gruner,  in  six  categories,  which  differ  in  the  quantity  and  quality  of  the  coke 
they  furnish  and  in  their  calorific  powers.  The  normal  limits  for  each  of  these 
classes  are  indicated  in  Table  XXXVIII  (p.  311),  the  data  in  which  are  referred 
to  the  pure  fuel  (free  from  moisture  and  ash). 


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310 


COAL 


TABLE    XXXVIII 
Limits  of  Composition  of  Coals  (Gruner) 

(The  values  refer  to  dry,   ashless  coal) 


Elementary 

Percentage  of 

No. 

Class, 

percentage  Composition. 

Ratio 
O  +  N 

Appearance  and 
quality  of  the  Coke. 

Pnl«» 

H 

MwO 

Volatile 

C 

H 

O  +  N 

(fixed 
carbon) 

Matters. 

I 

Dry     long-flame 

75-80 

5-5-4-5 

19-5- 

4-3 

50-60 

50-40 

Pulverulent  or 

coal    (non-cak- 

15-5 

only    slightly 

ing) 

coherent. 

2 

Fat,     long-flame 

80-85 

5-8-5 

14-2-10 

3-2 

60-68 

40-32 

Caked  but  very 

or  gas  coal 

porous. 

3 

Fat,    caking    or 

84-89 

5-5-5 

n-5-5 

2-1 

68-74 

32-26 

Caked,  somewhat 

furnace  coal 

porous. 

4 

Fat,   short-flame 

88-91 

5-5-4-5 

6-5-4-5 

about  i 

74-82 

26-18 

Caked  and  com- 

or caking  coal 

pact. 

5 

Lean,  short-flame 

90-93 

4-5-4 

5-5-3 

about  i 

82-90 

18-10 

Adherent  or  pul- 

or anthracitic  coal 

verulent. 

6 

Anthracite   . 

93-95 

4-2 

3 

about  i 

more 

less 

Pulverulent. 

than  90 

than  10 

The  calorific  power  of  coals,  referred  to  the  dry,  ashless  fuel,  varies  in  general 
from  7600  to  8900  cals.  * 

As  regards  the  uses  to  which  different  coals  are  especially  suited,  long  flame, 
non-caking  coal  (Class  i)  is  adapted  to  the  manufacture  of  gas  and  particularly 
for  reverberatory  furnaces.  Gas  coal  (Class  2)  is  preferred  for  making  gas,  since, 
in  comparison  with  the  preceding,  it  gives  volatile  matters  richer  in  carbon 
and  hence  more  illuminating,  although  in  lower  yield.  Fat,  caking  or  furnace 
coal  is  suitable  for  use  in  reverberatory  furnaces  and  for  making  metallurgical 
coke  ;  for  the  latter  purpose  the  short-flame  caking  coals  are  particularly  adapted. 
Finally,  the  lean,  short-flame  or  anthracitic  coals  and  the  anthracites,  owing 
to  their  slow  combustion  and  to  the  little  smoke  they  give,  are  used  for  domestic 
purposes  and  for  the  heating  of  boilers,  where  a  slow,  quiet  fire  is  required. 
Further,  in  consequence  of  the  paucity  of  their  volatile  matters,  the  anthracites 
may  be  used  directly  in  blast  furnaces  instead  of  coke. 

For  industrial  purposes  coal  should  not  contain  more  than  2-3  %  of  sulphur. 
The  best  coals  contain  3-8%  of  ash  and  the  proportion  may  be  12%  in  good 
coal,  but  coal  with  more  than  this  is  regarded  as  medium  or  bad.  The  moisture 
of  unwashed  coal  should  not  exceed  3%. 

Table  XXXIX  gives  the  analytical  results  for  a  number  of  bituminous  coals 
and  anthracites. 


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ishire,  Wigan  :  Cannel  coal  1  . 

Rushy  Park  :  Steam  coal  1 
shire,  Denaby  Main  :  Engine  coal  * 
rdshure,  Rowhurst  :  Gas  coal 
)1,  Timsbury  :  Gas  coal  2  . 
ind,  Wilson  Navigation  :  Engine  cot 
Hamilton  Splint  :  Gas  coal 
Bent  :  Cannel  coal  2 
Ayrshire  :  Main,  Steam  coal  1 

Grand'  Combe  (Card)  :  Coke  coal  * 
Blanzy  (Cote  d'Or)  :  Non-caking,  long-fla 
coal  *  
Creuzot  (Cote  d'Or)  :  Anthracitic  coal* 
Commentry  (Allier)  :  Gas  coal  *  .  . 
Isere  :  Anthracite  1  

Belgian. 

Grand  Buisson  (Mons)  :  Caking  coal  1  . 
Belle  Vue  (Mons)  :  Short-flame,  caking  cc 
Saint  Martin  (Charleroi)  :  „  „* 
Beaulet  (Charleroi)  :  Anthracitic  coal  1 

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COKE— AGGLOMERATED  FUELS  315 


COKE 

Ordinary  heating  coke,  obtained  as  a  secondary  product  in  the  manu- 
facture of  illuminating  gas  from  long-flame  bituminous  coal,  forms  more 
or  less  opaque,  highly  porous  lumps  of  a  grey  colour.  Metallurgical  coke, 
which  is  obtained  from  a  fat,  short-flame  coal,  is  resistant,  sonorous  and 
pale  grey  with  metallic  lustre.  In  every  case,  coke  consists,  apart  from 
ash,  essentially  of  carbon. 

*** 

Unwashed  coke  should  contain  only  1-2  %  of  moisture  ;  if  washed  and  air- 
dried  it  may  contain  as  much  as  5-6%.  With  certain  cokes  the  ash  may  amount 
to  20%,  but  good  samples  usually  contain  4-10%. 

Further,  coke  usually  contains  83-90%  C,  0-3-2%  H,  2-6%  O  and  1-2% 
N  ;  the  proportion  of  sulphur  may  reach  2-5%,  but  for  metallurgical  coke  the 
usual  requirement  is  that  it  shall  not  exceed  i%.  With  cokes  not  excessively 
rich  in  ash,  the  calorific  power  varies  from  7000  to  8000  calories. 

In  England  it  is  required  that  a  good  metallurgical  coke  should  not  contain 
more  than  4%  of  water,  8%  of  ash  and  0-5%  of  sulphur,  and  that  its  calorific 
power  should  be  about  8oco  cals. 


AGGLOMERATED    FUELS 
(Briquettes) 

These  vary  in  quality  with  the  coal  and  agglutinating  material  used 
in  their  manufacture.  Bituminous  coal  is  the  more  commonly  employed 
and  pitch  is  mostly  taken  to  act  as  cohesive,  although  many  other  materials 
have  been  proposed. 

Briquettes  are  Usually  brick-shaped,  but  cylinders,  sometimes  per- 
forated to  facilitate  access  of  air,  and  ovoid  forms  are  also  made 

With  these  fuels,  in  addition  to  the  determinations  given  under  the 
heading  "General  methods,"  it  is  important  to  ascertain  the  cohesion  or 
compactness.  This  may  be  done  with  a  special  apparatus,  or  by  a  crushing 
test  normal  to  the  largest  face  (with  brick-shaped  briquettes). 

In  some  cases  also  the  resistance  to  heat  is  tested,  in  order  to  find  out 
if  the  briquettes  soften  when  kept  for  a  certain  time  at  a  definite  tempera- 
ture (e.g.,  6  hours  at  60°). 

The  determination  of  the  'pitch  used  as  agglutinant  may  be  carried  out 
approximately  by  extraction  in  a  Soxhlet  apparatus  with  carbon  disulphide 
until  the  latter  ceases  to  become  coloured  (this  usually  requires  at  least 
10  hours),  evaporating  the  carbon  disulphide  and  weighing  the  residue 
after  drying  at  120°.  In  this  way,  however,  only  50-60%  of  the  pitch 
actually  used  is  extracted. 

*  * 

The  conditions  to  be  satisfied  by  briquettes  vary  with  the  quality  and  with 
the  uses  to  be  made  of  them.  Tn  general  it  is  required  that  they  should  be  homo- 


316  AGGLOMERATED   FUELS    (BRIQUETTES) 

geneous,  not  too  brittle,  almost  odourless  and  non-hygroscopic,  and  that  they 
do  not  break  up  in  the  furnace  or  give  too  much  smoke  when  burning. 

As  regards  briquettes  of  bituminous  coal,  the  amount  of  pitch  used  varies 
between  5  and  10%  and  is  commonly  about  8%.  The  moisture  should  not 
exceed  5%  and  the  ash,  which  in  good  qualities  is  often  not  more  than  7%, 
should  not  be  more  than  9-10%  ;  the  volatile  matters  vary  from  14  to  24%, 
but  are  ordinarily  about  16%.  Good  bituminous  briquettes  should  not  contain 
more  than  1*2%  of  sulphur,  and  their  calorific  power  should  be  about  equal 
to  that  of  the  good  coal  from  which  they  are  made  and  in  general  should  not 
be  below  7500  cals. 


CHAPTER  VII 
GOAL    TAR 

AND    ITS    PRODUCTS 

During  the  dry  distillation  of  coal,  as  in  the  manufacture  of  illuminating 
gas  and  in  the  preparation  of  coke,  crude  tar  is  collected  as  a  secondary 
product.  When  subjected  to  further  treatment  this  gives,  on  distillation, 
tar  oils,  these  being  distinguished  according  to  the  temperature  at  which 
they  are  collected,  as  light,  medium,  heavy  and  anthracene  oils.  The  residue 
from  the  distillation  is  pitch.  From  the  light  oils  are  obtained,  by  further 
distillations,  benzene  (benzole)  and  the  toluenes  (toluoles),  which  are  used  in 
the  dye  and  explosive  industries  and  as  solvents.  The  medium,  heavy 
and  anthracene  oils  yield  other  products  of  industrial  importance,  such  as 
naphthalene,  anthracene,  carbolic  acid,  pyridine  bases  and  impregnating  oils. 
All  of  these  products  are  considered  separately  in  succeeding  paragraphs, 
the  tests  commonly  made  in  each  case  being  indicated. 

Sampling. — With  very  viscous  liquids,  such  as  crude  tar  and  heavy 
and  anthracene  oils,  it  is  not  easy  to  obtain  a  sample  exactly  representing 
the  mean  composition  of  the  whole  mass.  To  take  such  a  sample  from  the 
vessel  or  tank  containing  the  material,  use  is  made  of  a  metallic  dipping 
cylinder  4-5  cm.  wide  and  closed  at  the  bottom  by  a  plug  which  is  raised 
or  lowered  by  means  of  an  iron  wire  passing  through  the  cylinder  itself. 
The  cylinder  is  filled  several  times  and  all  the  samples  mixed  so  as  to  obtain 
as  representative  a  sample  as  possible.  With  a  non- viscous  liquid,  however, 
it  is  sufficient  to  mix  the  mass  before  extracting  the  sample. 

With  solid  products  such  as  naphthalene  and  anthracene,  the  mass 
must  be  examined  to  see  if  it  is  all  of  the  same  appearance,  and  samples 
should  be  drawn  from  different  parts  and  mixed  before  analysis. 

CRUDE    TAR 

This  is  a  dense,  black,  oily  liquid  with  a  characteristic  odour  due  to  the 
presence  of  aromatic  hydrocarbons,  phenols,  naphthalene  and  pyridine 
bases.  When  it  is  to  be  distilled,  the  tests  made  are  1-4  (below),  but  if  it  is 
to  be  used  as  a  fuel,  the  ash  content  and  the  calorific  power  are  determined 
as  with  mineral  oils  (q.v.). 

1.  Determination  of  the  Water. — Since  tar  exhibits  a  tendency  to 
allow  the  water  present  to  separate,  either  the  sample  should  be  taken 
immediately  after  the  whole  mass  has  been  mixed,  or  the  separated  water 

317 


318  CRUDE  TAR 

should  be  removed  with  a  pipette  and  measured,  the  value  given  by  the 
subsequent  determination  being  suitably  increased. 

In  a  glass  or  copper  distillation  flask,  a  weighed  quantity  of  100  grams 
of  the  well-mixed  sample  is  distilled  with  50  c.c.  of  benzene  (90%  and  50%) 
through  a  condenser.  The  distillation  is  carried  up  to  190°  in  about  half 
an  hour,  the  distillate  being  collected  in  a  graduated  cylinder  and  the  volume 
of  the  aqueous  layer  read  off.  Industrially,  the  water  is  determined  directly 
during  the  distillation  test  and  is  collected  with  the  light  oils,  from  which 
it  separates  on  standing,  so  that  it  may  be  easily  measured. 

2.  Determination  of  the  Specific  Gravity. — The  tar  is  first  com- 
pletely freed  from  water.     To  this  end  it  is  left  for  24  hours  in  a  closed  vessel 
in  a  bath  of  water  heated  to  a  temperature  not  higher  than  50°,  being  shaken 
from  time  to  time  to  facilitate  the  rising   of    the  drops  of  water  and  air 
bubbles.     When  the  layer  of  water  is  thoroughly  separated,  it  is  decanted 
or  siphoned  off  and  the  specific  gravity  of  the  residual  tar  determined  at 
15°  C.     With  a  fairly  mobile  tar,  an  ordinary  densimeter  or  picnometer  is 
used,  but  with  very  dense  tar  either  a  picnometer  for  solids,  with  a  wide 
mouth  and  a  ground  stopper  surmounted  by  a  tube  with  a  mark  on  it,  or 
an  ordinary  weighing  bottle  with  a  rill  in  the  stopper  l  may  be  used. 

3.  Determination    of    the    Free    Carbon . — According    to    Kohler's 
method,2  10  grams  of  the  tar  are  boiled  with  25  c.c.  of  acetic  acid  and  25 
c.c.  of  toluene  in  a  conical  flask  with  a  reflux  apparatus  and  the  hot  liquid 
filtered  through  two  filter-papers  reduced  to  equal  weight  and  placed  one 
inside  the  other.     The  residue  on  the  filter  is  washed  with  hot  toluene  until 
the  latter  passes  through  colourless,  the  two  filters  being  then  separated 
and  dried  at  about  120°  until  of  constant  weight.     The  difference  in  weight 
between  the  two  filters  gives  the  free  carbon. 

From  the  content  of  free  carbon  (c)  thus  obtained,  the  yield  of  a  tar 
in  pitch  of  a  definite  hardness  may  be  determined — knowing  the  proportion, 

100  c 

k,  of  free  carbon  in  the  pitch — -by  the  formula  x  =  —  —  - 

k 

Assuming  that,  for  a  good  pitch  of  medium  hardness,  k  is  28%,  a  tar  con- 
taining c%  of  free  carbon  will  give  x  —  (looc  -±-  28)%  of  such  pitch. 

4.  Fractional    Distillation. — Fractional    distillation   of   tar   presents 
difficulties  on  account  of  the  bumping,  which  is  due  mainly  to  the  presence 
of  water.     It  is,  therefore,  necessary  first  to  dehydrate  the  tar  as  completely 
as  possible  in  the  manner  indicated  above,  then  to  distil  from  a  flask  not 
more  than  half  full  and  to  heat  with  great  care  until  all  the  residual  water 
is  eliminated.     The  apparatus  used  for  the  distillation  of  mineral  oils  may 
be  employed  (see  Chapter  VIII).     It  is  also  advantageous  to  pass  through 
the  boiling  liquid  a  gentle  current  of  air  by  means  of  a  capillary  tube  dipping 
into  the  liquid,  the  boiling  being  thus  rendered  more  even.     During  the 
initial  stages  of  the  distillation  use  is  made  of  a  condenser,  which  is  removed 
when  the  distillate  tends  to  solidify^in  the  tube.     As  regards  the  limits  of 
temperature,  four  successive  fractions  are  usually  collected  : 

1  See  Lunge  :    Coal  Tar  and  Ammonia,  1916,  Part  I,  p.  520. 

2  Dingler's  Polyt.  Journ.,  1888,  270,  p.  233. 


CRUDE  LIGHT  TAR  OILS  319 

(1)  Up  to  170°— light  oils. 

(2)  From  170°  to  230° — middle  or  carbolic  oils. 

(3)  From  230  to  270° — heavy  or  creosote  oils. 

(4)  Above  270°  (distilled  without  thermometer) — green  or  anthracene 
oils. 

The  distillation  is  discontinued  when,  almost  all  the  tar  being  distilled, 
the  drops  passing  over  become  intensely  red.  The  residue  in  the  retort, 
representing  the  pitch,  is  weighed. 

Industrially  the  distillation  test  is  carried  out  on  larger  quantities  (0-5  to 
5  kilos)  in  a  metallic  vessel,  so  that  results  in  greater  accord  with  those  of  the 
works  may  be  obtained.1 


The  specific  gravity  of  coal  tar  (dry)  usually  varies  from  i-ioo  to  1-280,  but 
in  exceptional  cases  may  be  below  i .  The  composition  of  the  tar  varies  according 
to  the  character  of  the  coal  yielding  it  and  to  the  mode  of  heating  (whether  in 
vertical  or  horizontal  retorts),  and  similar  variation  is  shown  by  the  yield  of 
distillation  products.  Tar  contains  10-35%  °f  ^ree  carbon  and  the  quantity 
of  water  permissible  in  it  when  sold  to  the  distilleries  is  4-5%. 


CRUDE    LIGHT    TAR    OILS 

Analysis  of  these  products  includes  the  following  determinations  : 

1.  Determination  of  the  Specific  Gravity. — By  means  of  a  hydro- 
meter or  Westphal  balance  at  15°  C.  ,j 

2.  Distillation. — 100    c.c.    are    fractionally    distilled    from    a    glass 
or,   better,    copper   vessel   of   150   c.c.   capacity,  furnished   with  a   ther- 
mometer and  connected  with  a  condenser.     The  portion  passing  over  up 
to  120°  is  the  crude  benzole  (with  toluole,  etc.)  and  that  between  120°  and 
170°,  the  naphtha  (solvent  naphtha]  ;   the  residue  is  regarded  as  middle  oils. 
The  distillates  may  be  tested  by  the  reactions  for  detecting  the  presence 
of  any  light  petroleum  oils  (benzine)  or  oil  of  turpentine  (see  later  :  Benzole, 
3,  c,  and  also  Oil  of  Turpentine,  Vol.  II). 

3.  Determination    of   the    Phenols. — -The    fractions   obtained   from 
the  preceding  distillation  are  reunited,  the  containing  vessels  being  rinsed 
out  with  xylene  and  the  whole  introduced  into  a  500  c.c.  graduated  cylinder 
with  a  ground  stopper  and  repeatedly  shaken  with  100  c.c.  of  caustic  soda 
solution   (D  1-2).     After  being  left  at  rest  for  some  time,  the  volume  of 
soda  solution  underneath  is  read,  the  increase  in  its  volume  giving  the 
percentage  of  phenols  by  volume. 

For  a  more  exact  determination  the  alkaline  layer  is  collected  and 
evaporated  on  a  water-bath  until  addition  of  water  no  longer  produces 
turbidity.  When  cold,  the  liquid  is  acidified  with  hydrochloric  acid  and 
treated  with  sodium  chloride,  the  layer  of  phenols  which  separates  being 
measured. 

4.  Determination  of  the  Bases. — The  oil  freed  from  phenols  by  the 
treatment  just  described  is  repeatedly  shaken  with  30  c.c.  of  20%  sulphuric 

1  Lunge:  Technical  Methods  of  Chemical  Analysis  (London,  1911),  Vol.  II,  p. 
763- 


320  ANTHRACENE  OILS 

acid  in  a  graduated  cylinder,  the  increase  in  volume  of  the  lower  layer 
giving  the  percentage  by  volume  of  the  bases.  These  may  also  be  deter- 
mined directly  by  collecting  the  acid  liquid,  carefully  adding  to  it  a  large 
excess  of  caustic  soda  solution  (D  1-40),  and  measuring  the  bases  which 
separate. 


*  * 


The  specific  gravity  of  the  light  oils  usually  lies  between  0-900  and  0-950. 
Normal  oils  give  about  90%  of  distillate  up  to  200°  and  have  the  specific  gravity 
0-930  ;  they  contain  5-15%  of  phenols  and  1-3%  of  bases. 

MIDDLE    AND    HEAVY    TAR    OILS 

With  these  the  following  determinations  are  made  : 

1.  Determination  of  the  Specific  Gravity.  —  As  with  light  oils. 

2.  Distillation.  —  This  is  carried  out  either  with  the  product  as  it 
stands,  which  is  distilled  from  a  flask  with  a  long  side-  tube  but  no  condenser 
(to  prevent  crystallisation  of  naphthalene),  or  with  the  product  free  from 
naphthalene,  or  with  that  free  also  from  phenols  and  bases,  resulting  from 
determinations  3  and  4. 

3.  Determination  of  the  Crude  Naphthalene.  —  From  0-5  to  2  kilos 
of  the  oil  is  left  for  24  hours  at  15°  and  then  cooled  if  necessary  to  cause 
the  naphthalene  to  crystallise,  this  being  pumped  off  on  a  cloth  or  paper 
filter,  pressed  in  a  press  until  all  the  oily  part  is  removed  and  weighed. 
This  represents  the  crude  naphthalene,  of  which  the  melting  and  boiling 
points  may  be  determined. 

4.  Other  Determinations.  —  The  oil  free  from  naphthalene  is  treated 
with  caustic  soda  to  determine  the  phenols,  and  with  dilute  sulphuric  acid 
to  determine  the  pyridine  bases,  as  with  the  light  oils  (3  and  4). 


* 
*  * 


A  good  middle  oil  has  a  specific  gravity  not  less  than  i  ;  at  least  00%  of  it 
distil  below  260°,  and  it  contains  not  less  than  30%  of  crude  naphthalene  (b.p. 
210-220°).  The  naphthalene-free  oil  has  the  specific  gravity  0-99-1-01,  and 
contains  25-35%  of  phenols  (about  one-third  of  this  being  carbolic  acid)  and 
about  5%  of  bases. 

The  heavy  oils  have  a  mean  specific  gravity  1-04  and  distil  between  200° 
and  300°  ;  they  contain  mainly  naphthalene  and  other  solid  hydrocarbons, 
together  with  8-10%  of  phenols  (principally  cresols  and  higher  homologues) 
and  about  6%  of  pyridine  bases. 

ANTHRACENE    OILS 

The  analysis  of  anthracene  oils  includes,  besides  determinations  of  the 
specific  gravity  and  of  the  behaviour  on  distillation  —  -which  are  carried 
out  as  with  the  middle  oils  —  only  the  determination  of  the  anthracene, 
which  is  effected  by  transforming  it  into  anthraquinone  by  means  of  chromic 
acid  (see  later  :  Anthracene,  i  )  . 

* 
*  * 

Anthracene  oils  have  the  specific  gravity  about  i-i  and  boil  between  280° 
and  400°  ;  they  are  solid  at  the  ordinary  temperature  and  fluid  at  60°  and 
contain  2-5-3-5%  of  pure  anthracene  and  about  6%  of  higher  phenols. 


PITCH 


321 


PITCH 

This  exists  in  the  three  forms,  soft,  hard  and  extra  hard,  and  the  tests 
made  are  for  the  purpose  of  ascertaining  to  which  class  the  sample  belongs 
and  hence  to  what  uses  it  may  well  be  put. 

1  Determination  of  the  Specific  Gravity. — With  the  picnometer 
in  the  ordinary  way  for  solids  ;  very  hard  pitches  should  first  be  powdered. 

2.  Determination  of  the  Free  Carbon. — As  with  tar  (see  Crude  Tar, 
3,  P-  3i8). 

3.  Determination  of  the  Ash. — 2  or  3  grams  of  the  pitch  are  burnt 
in  a  porcelain  crucible  in  a  muffle  and  the  residue  weighed. 

4.  Determination  of  the  Volatile  Matter  and  Coke. — As  with  fuels 
(q.v.}.     It  is  important  to  note  the  appearance  of  the  coke — whether  swollen, 
compact  or  coked. 

5.  Softening  and  Melting  Temperatures. — These  serve  better  than 
other  tests  to  indicate  the  degree  of  purity  of  the  pitch.     In  a  beaker  of 
water  containing  about  half  a  litre  of  water  is  suspended  a  cube  of  the  pitch 
of  about  13  mm.  side  or  a  disc  4-5  mm.  thick  at  the  end  of  an  iron  wire, 
the  pitch  being  5  cm.  from  the  bottom.     A  thermometer  is  immersed  with 
the  bulb  at  the  same  depth  as  the  pitch  and  the  temperature  of  the  water 
raised  5°  per  minute.     From  time  to  time  the  pitch  is  withdrawn  to  ascertain 
how  it  behaves  when  pressed  between  the  fingers.     The  temperature  of 
incipient  softening  is  taken  as  the  lowest  at  which  the  pitch  can  be  twisted 
without  breaking,  while  the  temperature  of  softening  is  that  at  which  it  can 
be  moulded  between  the  fingers  without  force  and  the  melting  point  as  that 
at  which  it  begins  to  drop. 

6.  Distinction   between   Tar   Pitch,   other   Pitches   and   Natural 
Asphalt. — The  characters  of  these  products  are  as  follows  : 


Coal-tar 
Pitch. 

Vegetable  Pitch 
(Black  or  Marine 
Pitch). 

Petroleum 
Pitch. 

Stearine 
Pitch. 

Natural 
Bitumen. 

Black,  more 

Black,    with    an 

Black,  almosl 

Black,  odour 

Blackish,  usu- 

or less  stiff, 

odour    recalling 

odourless. 

of  fatty  sub- 

ally    solid 

with  an  odour 

that     of     vege- 

stances. 

and    hard, 

of  tar. 

table  tar. 

sometim  es 

soft. 

Slightly  soluble 

Very    soluble    in 

Almost  com- 

Insoluble    in 

Insoluble      in 

in      alcohol, 

alcohol,  giving  a 

pletely     in- 

alcohol and 

alcohol; 

the   solution 

brown    solution 

soluble      in 

part  ia  lly 

does  not  give 

giving     the 

containing  resin- 

petroleum 

soluble      in 

the  reactions 

reactions 

ous  matters  and 

ether. 

petroleum 

for  phenols. 

for  phenols  ; 

giving    the    re- 

ether. 

very  slightly 

actions  for  phen- 

soluble      in 

ols.     It    colours 

light    petro- 

potash   solution 

leum. 

brown. 

The    distillate 

The  distillate  has 

In  general  has 

Has  a  saponi- 

has  an  alka- 

an acid  reaction. 

no  saponifi- 

fication  num- 

line reaction. 

cation  num- 

ber  and    an 

ber. 

acid  number. 

Evolves  acro- 

lein        when 

heated. 

A.C. 


21 


322  IMPREGNATING  OILS 

The  specific  gravity  of  soft  pitches  is  usually  1-2 50-1 -265,  that  of  hard 
i -275-1 -280,  and  that  of  very  hard  1-275-1 -280.  For  pitch  from  gas  tar,  the 
carbon  content  is  rarely  less  than  25-30%,  and  for  that  from  vertical  retorts 
or  blast-furnaces,  5-7%.  The  ash  content  is  less  than  0-5%  for  gas  pitch  and 
more  than  i%  (6-10%)  for  that  from  blast-furnaces.  The  yield  of  coke  varies 
from  30  to  60%,  and  the  coke  has  a  more  or  less  porous  appearance  according 
to  the  type  of  pitch  from  which  it  is  derived  (very  porous  with  the  very  hard 
pitches,  less  so  with  the  others). 

As  regards  the  temperatures  of  softening  and  fusion,  the  following  limits 
may  be  taken  for  different  types  of  pitch  : 

Soft :   Softens  at  40°,  melts  at  50-60°. 

Hard  :  Softens  at  60°,  melts  at  70-80°. 

Very  hard  :  Softens  at  80-85°,  melts  at  90-120°. 

A  good  pitch  for  making  briquettes  should,  according  to  Spilker  *  have 
the  following  properties  :  not  more  than  0-5%  of  ash  ;  softening  point  between 
60°  and  75°  ;  solubility  in  aniline,  70-75%,  and  in  carbon  disulphide,  not  less 
than  70%  ;  yield  of  coke,  45%  ;  appearance  of  coke,  caking  and  not  too  much 
swollen. 


IMPREGNATING  OILS 

These  are  usually  creosote  oils  or  anthracene  oils,  freed  more  or  less 
completely  from  crystallisable  substances,  and  are  used  for  the  impregna- 
tion of  wood,  especially  railway  sleepers  and  telegraph  poles,  with  the 
object  of  preserving  it. 

In  general  they  are  brownish  red  or  blackish  liquids,  more  or  less  fluores- 
cent, somewhat  viscous,  and  with  a  more  or  less  marked  odour  of  the 
products  of  tar  distillation. 

The  principal  tests  to  be  made  are  : 

1.  Determination  of  the  Specific  Gravity. — By  means  of  a  hydro- 
meter or  Westphal  balance  at  15°  C. 

In  some  cases  measurements  are  made  at  higher  temperatures,  e.g.,  at  25, 
45>  5°°  C.  ;  the  temperature  used  must  be  indicated  in  the  report. 

2.  Distillation. — This  is  carried  out  in  a  tubulated  retort  of  about 
300  c.c.  capacity,  furnished  with  a  thermometer.     The  retort  is  charged 
with  100  c.c.  of  the  liquid  and  the  thermometer  bulb  arranged  at  about  2 
cm.  from  the  liquid,  which  is  heated  so  that  120  drops  per  minute  pass 
over ;    the  different  fractions  are  measured. 

3.  Determination    of   the    Phenols    and    the    Naphthalene. — The 
fractions  obtained  as  under  2  are  reunited  in  a  graduated  cylinder,  shaken 
repeatedly  with  100  c.c.  of  caustic  soda  solution  (D  1-15)  saturated  with 
sodium  chloride  and  then  left  to  settle  ;  the  increase  in  volume  of  the  soda 
solution  gives  the  percentage  of  phenols.     In  the  supernatant  oily  layer 
the  naphthalene  is  determined  by  cooling  (to  15°)  in  the  manner  indicated 
for  middle  oils. 

4.  Test   for   the  Presence  of   Solid    Substances. — 20  c.c.  should 
remain  liquid  when  heated  to  40°  and  when  shaken  with  20  c.c.  of  pure 
benzene  :    when  filtered  through  paper,  the  solution  thus  obtained  should 
not  leave  a  brown  mark  on  the  filter. 

1  Lunge:    Coal-Tar  and  Ammonia  (London,  1916),  p.  542. 


BENZOLES 


323 


5.  Other  Determinations. — The  temperature  of  inflammability  and 
the  viscosity  may  also  be  required  ;  these  are  ascertained  as  with  heavy 
mineral  oils  (see  these:  Chapter  VIII). 


* 
*  * 


The  composition  of  impregnating  oils  varies  according  to  the  conditions  of 
the  contract.  Thus,  a  specific  gravity  of  1-03-1-10  or  of  1-05  at  50°  is  required  : 
a  content  of  5-30%  of  naphthalene  ;  a  content  in  phenols  of  5-10%,  and  various 
boiling  points.1 


BENZOLES 

Commercial  benzoles  from  the  tar  industry  are  mixtures  in  varying 
proportions  of  benzene,  toluene  and  xylenes,  and  contain  also  ethylbenzene, 
trimethylbenzenes  and  other  homologues  of  benzene.  The  separate  pure 
hydrocarbons  are  obtained  by 
further  and  complicated  rectifica- 
tions. 

The  rectified  benzoles  are  colour- 
less, limpid  liquids  with  a  character- 
istic, pleasant  odour  ;  any  turbidity 
indicates  presence  of  water. 

The  tests  and  determinations  to 
be  made  are  : 

1.  Determination       of      the 
Specific   Gravity. — By  the    West- 
phal  balance,  densimeter  or   picno- 
meter. 

2.  Distillation.  —  This     test, 
which    serves  to  characterise  com- 
mercial   benzoles,    may   be    carried 
out  in  an  ordinary  distillation  flask, 
similar  to  that  used  for  light  mineral 
oils.      Industrially,  however,  the  de- 
tailed instructions    given  by  Krae- 
mer  and  Spilker2  are    followed,  so 
that    comparable    results    may    be 

obtained.  FIG  ^ 

The  distillation  apparatus  used  is 

represented  in  Fig.  37  and  consists  of  a  copper  vessel  A,  0-6-07  mm-  thick, 
about  150  c.c.  in  capacity  and  of  the  dimensions  indicated.  To  the  mouth 
of  the  vessel  is  fitted  a  dephlegmator  B,  14  mm.  wide  and  150  mm.  long, 
furnished  with  a  bulb  and  with  a  side-tube,  8  mm.  in  diameter,  fixed  almost 
at  right  angles.  A  thermometer,  reading  to  0-1°  or  0-05°  (for  commercial 
benzoles)  is  introduced  so  that  its  bulb  is  in  the  centre  of  the  bulb. 

1  For  greater  details,  see  Lunge  :   Coal-Tar  and  Ammonia  (London,  1916),  p.  695  ; 
Allen  :    Commercial  Organic  Analysis,  4th  edit.,   1910,  Vol.  Ill,  p.  368. 

2  Muspratt  :    Chemie,  4th  edit.,  1905,  Vol.  VIII,  p.  34. 


324 


BENZOLES 


The  copper  vessel  rests  on  a  circular  aperture,  50  mm.  in  diameter,  in 
a  piece  of  asbestos  card  E,  supported  on  an  oven  closed  at  the  sides  and 
provided  at  its  upper  part  with  four  10  mm.  holes  to  allow  of  the  circulation 
of  the  air.  The  heating  is  effected  by  a  Bunsen  burner  of  7  mm.  aperture. 

The  lateral  tube  of  the  dephlegmator  is  connected  with  a  condenser  D, 
800  mm.  long,  inclined  so  that  the  top  end  is  100  mm.  higher  than  the  free  end. 

With  this  apparatus  100  c.c.  of  the  liquid  are  distilled  in  such  a  manner 
that  5  c.c.  distil  over  per  minute  (2  drops  per  second),  fractions  passing 
over  at  different  temperatures  (up  to  100°,  120°,  145°,  160°,  175°,  190°, 
according  to  the  different  types  of  benzole)  being  collected  in  a  graduated 
cylinder  and  measured. 

For  exact  determinations  it  is  necessary  to  take  account  of  the  atmospheric 
pressure,  bearing  in  mind  that  for  pressures  between  720  and  780  mm.  the 
percentages  given  by  the  distillation  should  be  diminished  by  0-033  for  90% 
benzoles  and  by  0-077  for  50%  benzoles  for  each  millimetre  of  pressure  below 
the  normal  pressure  of  760  mm.  and  increased  by  the  same  amounts  for  each 
millimetre  above  760  mm. 

3.  Determinations  of  the  Separate  Hydrocarbons. — To  separate 

and  estimate  approximately  the  different  hydrocarbons  contained  in  com- 
mercial benzole,  the  latter  must  be  fractionally 
distilled  in  a  manner  rather  different  from  that 
just  described,  a  moderately  large  amount  of  sub- 
stance being  treated  in  an  apparatus  furnished 
with  an  efficient  dephlegmator.  Use  is  generally 
made  of  a  copper  vessel  of  the  form  and  dimensions 
indicated  (in  millimetres)  in  Fig,  38,  a  six-bulb 
Le  Bel-Henninger  fractionator,  60  cm.  long,  being 
fitted  to  it.  The  fractionator  is  provided  with  a. 
thermometer  and  joined  to  a  condenser,  and  i  kilo 
of  the  product  is  distilled  at  the  same  rate  as  in  2 
(above),  the  different  fractions  being  collected  in 
tared  receivers,  which  are  subsequently  reweighed. 
The  separation  of  the  different  hydrocarbons 
may  be  effected  by  further  fractional  distillations, 
regard  being  paid  to  the  boiling  points,  which  are 
as  follows  :  benzole,  80-81°  ;  toluole,  no— in0  ; 
xyloles,  138—142°  (o-xylene,  142°  ;  m-xylene,  139- 

140° ;     p-xylene,    138-139°)  ;     ethylbenzene,     137° ;     trimethylbenzenes, 

I63-I750. 

The  fractionation  of  the  different  commercial  products  is  carried  out  on  the 

basis  of  the  following  temperature  limits  : 


FIG.  38 


First  fraction 

Benzole 

Intermediate  fraction    . 

Toluole 

Xyloles 

Higher  homologues,  etc. 


Benzole        Pure  commercial 
(50%  and  90%):        Benzole. 


up  to  79° 

79-85 

85-105 

105-115 


residue 


up  to  79C 
79-81 


residue 


Toluole. 


up  to  109° 


109-110-5 
residue 


Xyloles. 


up  to  135' 


135-145 


residue 


BENZOLES  325 

The  separation  of  the  three  xyloles  (xylenes),  which  is  usually  not  required, 
cannot  be  effected  by  means  of  fractional  distillation,  their  boiling  points  being 
too  similar.  The  respective  quantities  may,  however,  be  determined  approxi- 
mately by  regarding  the  distillate  between  135°  and  137°  as  ^-xylene,  that 
between  137°  and  140°  as  w-xylene,  and  that  between  140°  and  145°  as  o-xylene  ; 
these  limits  refer  to  uncorrected  temperatures,  i.e.,  those  indicated  by  a  ther- 
mometer with  its  scale  only  partially  immersed  in  the  vapour. 

4.  Detection  and  Estimation  of  Impurities. — The  impurities  of 
commercial  benzoles  are  principally  carbon  disulphide,  thiophene,  paraffin 
hydrocarbons  and  naphthalene. 

(a)  CARBON  DISULPHIDE.    This  is  detected  by  shaking  about  10  c.c.   of 
the  benzole  or,  better,  of  the  first  fractions  of  its  distillate,  with  5  or  6  drops 
of  phenylhydrazine  and  leaving  the  mixture  at  rest  for  an  hour.     In  presence 
of  as  little  as  0-2%  of  carbon  disulphide,  a  white  precipitate  of  phenylhydra- 
zine phenylsulphocarbazinate  is  formed. 

For  the  determination,  the  ammonium  xanthate  (Hoffmann)  reaction  is 
used  : 

A  mixture  of  50  grams  of  the  benzole  with  50  grams  of  alcoholic  potash 
solution  (n  grams  of  KOH  in  90  grams  of  absolute  alcohol)  is  left  for  some 
hours  at  the  ordinary  temperature  and  is  then  shaken  with  100  c.c.  of  water. 
The  aqueous  layer  is  separated  from  the  benzole,  which  is  washed  two  or 
three  times  with  water,  the  total  aqueous  liquid  being  made  up  to  400  c.c. 
In  this  solution,  or  an  aliquot  part  of  it,  the  potassium  xanthate  formed  is 
determined  volumetrically  by  means  of  a  standard  copper  solution  (12-468 
grams  of  crystallised  copper  sulphate  per  litre). 

This  is  effected  by  acidifying  the  aqueous  liquid  containing  the  xanthate 
with  acetic  acid  and  then  adding  the  copper  sulphate  solution  until  the 
copper  is  in  excess,  i.e.,  until  a  drop  of  the  liquid  gives  the  brown  coloration 
with  potassium  ferrocyanide.  The  number  of  c.c.  used,  multiplied  by 
0-0076,  gives  the  percentage  of  CS2  in  the  aqueous  liquid  and  from  this  the 
percentage  in  the  benzole  may  be  calculated. 

(b)  THIOPHENE.     This  is  detected  by  the  indophenine  reaction.     To  a 
few  granules  of  isatin  in  a  porcelain  basin,  a  few  c.c.  of  pure  cone,  sulphuric 
acid  are  added  and  then  the  benzole,  the  liquid  being  covered  with  a  clock- 
glass  and  left  to  itself  for  some  hours  :  in  presence  of  thiophene,  blue  rings 
form  around  the  isatin  granules. 

Only  benzoles  guaranteed  free  from  thiophene  are  tested  for  the  latter. 

(c)  PARAFFIN    HYDROCARBONS    (benzines).    These   are    determined   by 
transforming  the  benzoles  into  the  soluble  sulpho-acids  (Kraemer  and  Spil- 
ker)  l :   200  grams  of  the  benzole  are  shaken  for  15  minutes  in  a  separating 
funnel  with  500  grams  of  fuming  sulphuric  acid  (20%  S03),  cooled  if  necessary 
and  left  for  two  hours.     The  sulphuric  acid  is  removed  and  the  operation 
repeated  twice.     The  residual  unattacked  oil  floating  in  the  sulphuric  acid 
represents  almost  the  whole  of  the  paraffin  hydrocarbons  (including  naph- 
thenes)  contained  in  the  200  grams  of  benzole. 

1  Muspratt :    Chemie,  4th  edit..  Vol.  VIII,  p.  34. 


326  BENZOLES 

For  exact  determinations,  the  hydrocarbons  remaining  suspended  in  the 
sulphuric  acids  employed  should  be  collected.  The  acid  liquors  are  poured 
slowly  and  with  shaking  on  to  an  equal  weight  of  pounded  ice  in  a  flask,  the 
temperature  never  exceeding  40°.  The  liquid  thus  obtained  is  distilled  and 
the  oil  separating  at  the  surface  of  the  first  50  c.c.  of  distillate  added  to  the 
quantity  determined  directly.  The  total  oil  thus  obtained  is  repeatedly  purified 
with  fuming  sulphuric  acid  (20%  of  anhydride)  in  lots  of  30  grams  each  until 
no  further  diminution  in  volume  takes  place.  It  is  then  washed  with  water 
and  measured,  the  volume,  divided  by  2,  giving  the  quantity  of  paraffin  hydro- 
carbons in  100  of  the  benzole. 

(d)  NAPHTHALENE.  10  c.c.  of  the  benzole  are  allowed  to  evaporate 
spontaneously  in  a  glass  dish,  any  naphthalene  present  remaining  crys- 
tallised on  the  walls  of  the  dish. 

5.  Degree  of  Refining. — Benzoles  may  contain  larger  or  smaller  quan- 
tities of  resinous  substances  not  completely  removed  by  refining.  The 
presence  of  these  substances  may  be  detected  as  follows : 

(a)  WITH  SULPHURIC  ACID.    5  c.c.  are  added  to    5  c.c.   of   cone,   sul- 
phuric acid  in  a  cylinder  with  a  ground  stopper,  the  mixture  being  shaken 
for  two  or  three  minutes  and  the  colour  of  the  acid  observed.     Pure  pro- 
ducts do  not  colour  the  acid  at  all,  and  commercial  products  colour  it  pale 
yellow  or  brown  according  to  the  extent  to  which  refining  has  been  carried. 
The  coloration  may  be  measured  by  comparison  with  solutions  of  potassium 
dichromate  in  sulphuric  acid. 

(b)  WITH    BROMINE.     5    c.c.   of    the  benzole  are  mixed  in  a  beaker 
with  10  c.c.  of  dilute  sulphuric  acid  (i  :  5)  and  a  decinormal  potassium 
bromide  and  bromate  solution  (9-9167  grams  KBr  +  2-7833  grams  KBrO3 
per  litre)  run  in,  slowly  and  with  shaking,  at  intervals  of  five  minutes  until 
the  bromine  liberated  no  longer  undergoes  absorption ;    this  is  shown  by 
the  orange-yellow  coloration  of  the  benzole  and  by  the  blue  colour  imparted 
to  starch-iodide  paper.     The  degree  of  refining  is  in  inverse  ratio  to  the 
amount  of  bromine  absorbed  (i  c.c.  N/io-solution  —  0-008  gram  Br).     The 
loss  during  further  refining  will  be  i%  per  0-2  c.c.  of  the  bromine  solution 
used. 

*** 

The  benzoles  most  commonly  found  on  the  market  may  come  from  the  dis- 
tillation of  light  tar  oils  or  from  the  distillation  of  the  washing  oils  obtained 
by  exhaustion  of  the  gas  from  the  manufacture  of  coke  or  coal  gas  by  means 
of  heavy  oils.  These  are  mixtures  in  varying  proportions  of  benzene  and  higher 
homologues.  Examples  of  the  more  important  characters  of  these  products 
are  as  follows  (Spilker)  : 


NAPHTHALENE 


327 


TABLE    XL 
Character  and  Composition  of  Benzoles 


Composition. 

Mark  and 
Denomination. 

Specific  Gravity 
at  15°  C. 

Percentage  of 
Distillate  at  different 
temperatures. 

Ben- 

Tolu- 

Xyl- 

Higher 

zole. 

ole. 

oles. 

I  (90%  benzole)    . 

0-880-0-883 

9°~93%  UP  to  1  00° 

84 

13 

3 

_ 

II  (50%  benzole).      . 

0-875-0-877J 

5°~53%  up  to  100° 
9°~93%  UP  to  120° 

43 

46 

II 

— 

Ill         

0-870-0-872 

90%  at  100-120° 

15 

75 

10 

—  • 

IV  

0-872—0-876 

90%  at  120—145° 



2^ 

7o 

5 

V  (solvent  naphtha)  . 

0-874-0-880 

90%  at  130-160° 

— 

5 

70 

25 

VI 

0-890-0-910 

90%  at  145-175° 

— 

— 

35 

65 

Heavy  benzole 

0-920-0-945 

90%  at  160-190° 

—  -. 

5 

95 

These  benzoles  contain  varying  proportions  of  impurities.  Thus,  thiophene 
is  always  present  in  the  earlier  of  the  above  marks  and  carbon  disulphide  occurs 
to  the  extent  of  0-2-1  %  in  benzole  I  and  0-0-5%  in  benzole  II,  whilst  it  is  usually 
absent  from  succeeding  marks.  In  marks  I,  II  and  III,  the  amount  of  paraffin 
hydrocarbons  is  at  most  i%,  and  in  other  marks  rather  more.  Pure  benzoles 
are  coloured  by  o-i  c.c.  of  the  bromide-br ornate  solution,  but  the  commercial 
products  require  0-6-1%. 

As  regards  the  behaviour  of  the  principal  commercial  products  on  fractional 
distillation  with  a  rectifier  for  the  separation  of  the  individual  hydrocarbons 
(see  above,  3),  the  following  serve  as  examples  : 


First  fraction 

Benzole 

Intermediate  fraction  . 

Toluole         .... 

Xyloles         ....     | 

Higher  homologues,  etc.        .     J 

The  proportions    of   the   three    isomerides  in  commercial  xylole  are  about 
76-5  of  m-,  15  of  p-  and  5  of  o-xylene. 


Pure  com- 

Com-           Com- 

Benzole 

Benzole 

mercial 

mercial        mercial 

I. 

II. 

Benzole. 

Toluole.         Xylole. 

1-0% 

o-3% 

o-5%   ) 

78-8% 

18-3% 

98-0%    \ 

0-3% 

-    1-3% 

10-0% 

47-5%  ^ 

} 

*   J  /O 

8-0% 

237% 

T  -CO/ 

97-3%   . 

2-2%     ] 

10-2%    J 

1  5  /o   i 

_..o/         96-5% 
24/o          2.20/ 

NAPHTHALENE 

This  is  marketed  in  different  degrees  of  purity  :  crude,  coloured  brown 
by  tar  oils  and  other  impurities,  and  moderately  pure,  in  more  or  less  large, 
white  or  faintly  yellow,  lamellar  crystals.  The  tests  usually  made  to 
determine  the  purity  are  as  follows  : 

1.  Melting  and  Solidification  Points. — These  are  determined  by 
means  of  Shukoff's  apparatus  (see  Chapter  on  Mineral  Oils,  Solid  Paraffin, 
2),  the  inner  test-tube  being  half  filled  with  the  fused  naphthalene  and  a 
thermometer  reading  to  0-1°  immersed  in  it.  On  immersion  the  ther- 
mometer bulb  becomes  covered  with  a  layer  of  solidified  naphthalene  ;  it 


328  ANTHRACENE 

is  then  stirred  until  this  layer  melts  and  the  temperature  noted,  this  indi- 
cating approximately  the  melting  point.  The  fused  mass  is  then  stirred 
with  the  same  thermometer  until  naphthalene  crystals  again  begin  to  form 
and  the  column  of  the  thermometer  remains  stationary  for  some  time.  This 
is  the  solidifying  point,  which,  with  pure  naphthalene,  corresponds  with 
the  melting  point. 

2.  Presence  of  Oily  Products. — A  packet  of  50  grams  of  the  naphtha- 
lene wrapped  in  several  thicknesses  of  filter-paper  is  subjected  in  a  press 
to  a  pressure  of  about  150  atmos.  for  10  minutes,  the  paper  being  then 
examined  to  see  if  it  is  stained  by  the  oil  absorbed. 

3.  Behaviour  towards  Petroleum  Ether. — 2  grams  of  the  naphtha- 
lene are  treated  in  a  test-tube  with  light  petroleum  to  see  if  a  clear,  colourless 
solution  is  obtained. 

4.  Behaviour  towards    Sulphuric    Acid. — -4   grams   are   heated   in 
a  test-tube  in  a  water-bath  with  4  grams  of  cone,  sulphuric  acid  until  a 
clear  solution  is  obtained,  the  colour  being  observed.     The  sulphuric  acid 
solution  is  poured  into  about  40  c.c.  of  water  to  ascertain  if  the  whole  remains 
clear  and  colourless. 

5.  Stability  towards  Light. — 2    grams  of    the  naphthalene    on    a 
clock-glass  are  left  for  1-2  hours  in  a  desiccator  over  cone,  nitric  acid  (not 
fuming),  the  naphthalene  being  then  examined  to  see  if  it  has  remained 

unaltered  or  if  it  is  coloured. 

* 
*  * 

Pure  commercial  naphthalene  is  white  or  slightly  yellow  and  melts  at  79-6- 
79-8°  ;  it  should  not  mark  paper  (test  2)  and  should  volatilise  completely  if 
heated  on  a  water-bath  ;  test  3  should  yield  a  clear  solution,  at  most  pink  or 
reddish,  which  should  remain  clear  on  dilution  ;  it  should  dissolve  completely 
in  petroleum  ether  (test  4)  and  should  remain  unchanged  when  subjected  to 
test  5  (slightly  impure  naphthalene  becomes  pale  pink). 


ANTHRACENE 

Commercial  anthracene  is  always  impure,  containing  principally  naph- 
thalene, methylanthracene,  carbazole,  paraffin  wax,  phenanthrene,  etc.  The 
technical  examination  of  crude  anthracene  is  limited  to  the  determination 
of  the  anthracene  content  and  to  tests  for  the  presence  of  impurities  which 
are  harmful  in  the  coal-tar  colour  industry. 

1.  Determination  of  the  Anthracene. — Luck's  method,  based  on 
the  oxidation  of  anthracene  to  anthraquinone  by  means  of  chromic  acid, 
is  usually  employed.  In  a  flask  with  a  capacity  of  about  half  a  litre,  fitted 
with  a  tapped  funnel  and  a  reflux  condenser,  a  boiling  solution  of  I  gram 
of  the  anthracene  in  45  c.c.  of  glacial  acetic  acid  is  treated  with  a  solution 
of  15  grams  of  crystallised  chromic  acid  in  10  c.c.  of  glacial  acetic  acid  and 
10  c.c.  of  water,  this  liquid  being  added  in  small  quantities  so  that  the  whole 
addition  requires  about  2  hours.  The  solution  is  boiled  for  two  hours 
longer,  then  left  to  itself  for  12  hours,  next  mixed  with  400  c.c.  of  cold  water 
and  left  at  rest  for  3  hours.  The  precipitated  anthraquinone  :.s  collected 
on  a  filter  and  washed  first  with  cold  water,  then  with  faintly  alkaline 


ANTHRACENE  329 

boiling  water  (i  gram  KOH  per  litre)  until  the  filtrate  no  longer  becomes 
turbid  on  acidification  and  finally  with  boiling  water  until  the  alkalinity 
is  removed.  The  contents  of  the  filter  are  washed  by  means  of  a  fine  water 
jet  into  a  small  porcelain  dish,  the  water  being  evaporated  and  the  residue 
dried  at  100°  and  heated  for  10  minntes  on  a  boiling  water-bath  with  10 
c.c.  of  fuming  sulphuric  acid  (D  1-88).  The  dish  is  subsequently  left  in  a 
moist  place  for  12  hours,  the  contents  diluted  with  200  c.c.  of  cold  water, 
arid  when  cold  the  anthraquinone  filtered,  washed  as  before,  placed  in  a 
tared  dish,  evaporated,  dried  at  100°  and  weighed.  For  greater  exactness 
the  anthraquinone  is  evaporated  and  the  residual  ash  determined  :  anthra- 
quinone x  0-8558  =  anthracene. 

2.  Detection  of  Impurities. — Among  the  more  common  impurities 
which  are  harmful  in  certain  applications  of  crude  anthracene,  e.g.,  in  the 
preparation  of  alizarin,  are  methylanthracene,  carbazcle,  paraffin  wax 
and  phenanthrene.  These  substances  are  detected  as  described  in  the 
following  paragraphs ;  for  their  quantitative  determination,  which  is 
carried  out  only  rarely  and  for  special  purposes,  special  works  must  be 
consulted.1 

(a)  METHYLANTHRACENE.    When  anthracene  containing  methylanthra- 
cene is  oxidised  by  chromic  acid,  as  described  above,  methylanthraquinone 
is  produced,  this  forming  threads  variously  twisted  rather  than  needles 
like  anthraquinone.     Methylanthraquinone  is  distinguished  from  the  latter 
also  by  its  great  solubility  in  benzene. 

(b)  CARBAZOLE.    The  anthracene  is  extracted  with  ethyl  acetate,  the 
solution  evaporated,  and  the  residue  treated  with  a  few  drops  of  ethyl 
acetate  to  which  are  added  some  drops  of  nitrobenzene  and  a  little  phenan- 
threnequinone.     The  presence  of  carbazole  is  shown  by  the  formation  of 
characteristic,  lamellar,  copper-coloured  crystals. 

(c)  PARAFFIN  WAX.     10  grams  of  anthracene  are  treated  with  100  c.c. 
of  ether,  the  ethereal  solution  separated  and  evaporated  and  the  residue 
treated  with  200  grams  of  fuming  sulphuric  acid  (20%  of  anhydride)  for 
three  hours  at  100°.     The  whole  is  poured  into  500  c.c.  of  water  and,  after 
cooling,  the  paraffin  wax  separated  at  the  surface  is  filtered  off,  washed 
well  with  water,  the  filter  allowed  to  dry  and  then  moistened  with  alcohol, 
and  the  paraffin  collected  by  adding  ether.     The  ethereal  solution  thus 
obtained  is  evaporated,  and  the  residue,  dried  at  105°,  gives  the  solid  paraffin 
in  the  sample. 

(d)  PHENANTHRENE.    A  certain  quantity  (i  kilo)  of  the  product  to  be 
tested  is  dissolved  in  the  hot  with  double  its  volume  of  toluene.     After 
cooling,  the  crystallised  anthracene  and  carbazole  are  separated  and  the 
mother-liquor  distilled,  the  portion  passing  over  between  300°  and  340° — 
which  contains   the  greater  part   of  the  phenanthrene — being  collected 
apart.     20  grams  of  this  fraction  are  boiled  for  half  an  hour  in  a   reflux 
apparatus  with  30  grams  of  picric  acid  and  300  c.c.  of  xylene  and  the  liquid 
allowed  to  cool  for  24  hours  ;    the  phenanthrene  picrate  which  separates 
is  crystallised  from  alcohol  in  reddish-yellow  needles  melting  at  145°. 

1  Lunge  :    Coal-Tar  and  Ammonia  (London,  1916),  p.  640. 


330  CARBOLIC  ACID 

Commercial  crude  anthracene  forms  masses  of  yellowish  to  brown  crystalline 
scales  with  an  odour  resembling  that  of  naphthalene  ;  according  to  the  degree 
of  purification,  it  contains  30-39%  of  anthracene  (English  anthracene  A  con- 
tains 40-50%). 

Pure  anthracene  forms  white,  tabular  crystals  with  a  blue  fluorescence, 
m.pt.  216-5°,  b.pt.  360°  ;  it  is  slightly  soluble  in  alcohol,  ether,  benzine,  carbon 
disulphide  and  cold  benzene,  and  readily  soluble  in  the  hot  in  benzene,  pyridine 
and  glacial  acetic  acid. 


CARBOLIC    ACID 

Crude  and  pure  carbolic  acid  are  on  the  market.  The  former  is  of  some- 
what variable  composition,  the  name  being  often  given  to  yellowish  or  dark 
brown  carbolic  oils  containing,  besides  varying  quantities  of  neutral  tar 
oils,  also  phenol  and  its  homologues  (mainly  cresols),  whereas  it  is  also 
used  to  designate  pale  red  products  rich  in  phenols  and  crystallising  more 
or  less  easily  when  cooled.  The  pure  product  is  colourless  or  pale  red, 
crystallisable  and  soluble  in  15  parts  of  water. 

In  very  impure  products  the  determination  of  the  phenols  and  neutral 
oils  is  carried  out  as  in  2  ;  in  the  others,  the  water,  solidification  point, 
and  the  solubility  are  determined  (3,  4  and  5)  and,  if  required,  the  quantita- 
tive estimation  according  to  Koppeschaar  (see  2). 

1 .  Characteristic  Reactions  of  the  Phenols. — The  following  reactions 
are  used  : 

(a)  The  aqueous  solution  of  a  phenol  gives  a  violet  coloration  with 
dilute  ferric  chloride   solution  (provided  mineral  and  organic  acids,  alcohol, 
ether  and  glycerine  are  absent). 

(b)  When  heated  gently  with  a  little  ammonia  and  a  few  drops  of  sodium 
hypochlorite,  the  aqueous  solution  of  a  phenol  gives  an  intensely  blue 
coloration. 

(c)  The  substance  is  shaken  with  water  and  the  aqueous  solution  treated 
with  bromine  water  :   if  it  is  a  phenol,  a  voluminous,  white  precipitate  of 
tiibromophenol,  at  first  flocculent  and  afterwards  crystalline,  is  produced. 
It  is  soluble  in  alkali  and  is  reprecipitated  on  acidification  of  the  alkaline 
solution.     The  tiibromophenol  reaction  (Landolt's  reaction)  is  sensitive  to 
about  i  part  in  44,000.     The  cresols  and  also  other  organic  compounds  are 
precipitated  by  bromine  water. 

(d)  A  very  sensitive  reaction  is  as  follows  :  About  i  c.c.  of  the  oil  to  be 
examined  is  shaken  with  i  c.c.  of  alcohol,  after  which  2  c.c.  of  water  and 
i  c.c.  of  about  i%  nitrazole  solution  (fresh)  are  added  and  again  shaken  : 
addition  of  a  little  caustic  potash  then  colours  the  aqueous  layer  an  intense 
red  in  presence  of  phenols. 

2.  Determination  of  Phenols  and  Neutral  Oils. — The  approximate 
determination  of  the  phenols  and  neutral  oils  in  crude  phenol  may  be  rapidly 
carried  out  by  shaking  a  measured  volume  of  the  sample  with  double  its 
volume  of  10%  sodium  hydroxide  solution  in  a  stoppered  graduated  cylinder, 
allowing  to  stand  and  reading  the  volume  of  the  neutral  oils  which  separate  ; 
subtraction  of  this  volume  from  that  of  the  substance  used  gives  the  quantity 
of  phenols.     To  facilitate  the  separation  of  the  neutral  oils  it  is  sometimes 


CARBOLIC  ACID  331 

convenient  to  dilute  the  sample  with  an  equal  volume  of  ligroin,  the  volume 
of  the  latter  being  then  subtracted  from  that  of  the  neutral  oils  separating. 

As  a  control,  the  alkaline  layer  may  be  separated,  acidified  in  a  graduated 
cylinder  and  the  volume  of  the  phenols  separating  read. 

More  exact  results  are  obtained  as  follows  :  120  grams  of  the  carbolic 
acid  to^  be  examined  are  distilled  until  only  about  8  grams  of  residue  remain 
in  the  flask,  the  distillate  being  dissolved  in  ether  and  shaken  repeatedly 
in  a  separating  funnel  with  10%  caustic  soda  solution.  The  total  alkaline 
liquid  is  washed  several  times  with  ether  and  then  acidified  with  hydro- 
chloric acid  diluted  with  an  equal  volume  of  water,  the  acid  liquid  thus 
obtained  being  extracted  repeatedly  with  ether  in  a  separating  funnel  to 
dissolve  the  phenols.  The  ethereal  solution  of  the  latter  is  washed  with 
water  and  placed  in  a  weighed  flask,  almost  all  the  ether  being  distilled  off  ; 
the  flask  is  then  closed  by  a  stopper  through  which  passes  a  vertical  bulb 
tube  and  a  thermometer,  and  the  last  portions  of  ether  then  evaporated, 
care  being  taken  that  the  temperature  does  not  exceed  100°  ;  the  cold  flask 
is  then  re-weighed,  the  increase  in  weight  representing  the  phenols. 

When  the  phenol  is  not  accompanied  by  its  homologues  (cresols,  etc.), 
it  may  be  determined  volumetrically  by  Seubert  and  Beckurts'  modification 
of  Koppeschaar's  method  : 

Use  is  made  of  a  solution  of  potassium  bromide  and  bromate  in  the 
proportions,  5KBr  +  KBr03,  which  in  presence  of  an  acid  liberates  bromine 
according  to  the  equation  :  5KBr  +  KBrO3  +  6HC1  =  6KC1  +  3Br2  + 
3H20.  About  i  gram  of  the  sample  (or  more,  if  poor  in  phenol)  is  weighed 
and  dissolved  in  water  to  a  litre,  25  c.c.  of  this  solution  being  vigorously 
shaken,  in  a  bottle  with  a  ground  stopper,  with  50  c.c.  of  potassium  bromide 
solution  (6  grams1  per  litre),  50  c.c.  of  potassium  bromate  solution  (1-671 
gram  per  litre),  and  5  c.c.  of  cone,  sulphuric  acid.  After  a  rest  of  15  minutes, 
10  c.c.  of  potassium  iodide  solution  (i25^grams  per  litre)  are  added  and  the 
iodine  liberated  titrated  with  decinormal  thiosulphate  in  presence  of  starch 
paste.  The  amount  of  phenol  contained  in  the  25  c.c.  of  solution  used  is 
found  by  multiplying  the  number  of  c.c.  of  decinormal  thiosulphate  used 
by  0-001567  and  subtracting  the  product  from  0-047. 

3.  Determination  of  the  Water. — (a)  In  crude  products,  this  is  effected 
by  distilling  100  c.c.  through  a  condenser  and  collecting  the  water  in  a 
graduated  cylinder  until  about  10  c.c.  of  phenols  are  collected  under  the 
water.     The  volume  of  the  upper  layer,  plus  5  c.c.,  gives  the  percentage  of 
water  in  the  product  distilled.     If  any  neutral  oils  are  floating  on  the  water, 
their  volume  is  subtracted. 

(6)  With  less  impure  prodttcts,  50  c.c.  of  the  substance  are  shaken,  in 
a  100  c.c.  graduated  cylinder  reading  to  0-2  c.c.,  with  25  c.c.  of  saturated 
salt  solution  and  the  aqueous  layer  allowed  to  separate  :  its  increase  in 
volume  indicates  the  amount  of  water  in  the  sample. 

4.  Determination  of  the  Solidification  Point. — This  is  made  in  the 
Shukoff  apparatus  (see  Mineral  Oils,  Paraffin,  2),  50  grams  of  the  fused 
phenol  being  introduced  into  the  inner  tube  and  allowed  to  cool  slowly 

1  Owing  to  the  slight  admixture  of  potassium  chloride,  6  grams  are  taken  instead 
of  5'95- 


332  PYRIDINE 

while  stirred  with  the  thermometer.  When  the  temperature  has  fallen  below 
the  solidifying  point  of  pure  phenol  (42°),  a  crystal  of  phenol  is  added,  the 
mass  beginning  to  crystallise  and  the  temperature  rising  and  then  remaining 
stationary.  The  highest  temperature  shown  represents  the  solidifying 
point  of  the  product  tested. 

5.  Solubility. — i  c.c.  of  the  material,  shaken  in  a  graduated  cylinder 
with  15  c.c.  of  water,  should  give  a  perfectly  clear  solution  if  the  product  is 
pure.  The  more  impurities  present,  the  more  insoluble  matter  remains. 

.**• 

Pure  carbolic  acid  has  the  melting  (solidifying)  point,  40-42  °,  and  the  boiling 
point,  183-184°.  Products  are  sold,  however,  with  lower  melting  points  (down 
to  32°),  this  resulting  from  the  presence  of  small  quantities  of  moisture  and 
cresols. 

PYRIDINE 

This  is  obtained  mainly  from  the  distillation  products  of  tar  and  is  sold 
ci  ude  or  pure.  Crude  pyridine  (pyridine  bases)  consists  essentially  of  bases 
of  the  pyridine  and  quinoline  groups,  etc.,  and  may  contain  other  aromatic 
bases,  pyrrole  and  ammonia.  It  is  a  colourless  or  yellowish  liquid  of  a 
penetrating  and  peculiarly  unpleasant  odour,  readily  volatile  and  inflam- 
mable, soluble  in  water.  Pure  pyridine  is  colourless  and  miscible  in  all 
proportions  with  water  or  ether,  b.pt.  116-117°,  D  0-980.  In  the  crude 
state  it  is  used  mainly  for  the  denaturation  of  spirits  for  industrial  purposes. 
The  following  are  the  tests  made  : 

1.  Colour. — The  colour  is  compared  with  that  of  a  solution  containing 
2  c.c.  of  decinormal  iodine  solution  to  a  litre,  using  two  glass  tubes  150  mm. 
long  and  15  mm.  in  diameter,  closed  with  glass  discs  (polarimeter  tubes 
may  be  used). 

A  colorimeter  is  more  practicable  (see  Mineral  Oils). 

2.  Behaviour  towards  Cadmium  Chloride. — 10  c.c.   of  a  solution 
of  i  c.c.  of  the  pyridine  in  100  c.c.  of  water  are  shaken  vigorously  with  5  c.c. 
of  a  solution  of  fused  cadmium  chloride  (5vgrams  in  100  of  distilled  water). 
A  copious,  crystalline  precipitate  should  form,  this  being  then  filtered  through 
a  9  cm.  filter-paper  (weighing  0-45-0-55  gram),  dried  for  an  hour  at  50-70° 
and  weighed. 

3.  Detection  of  Ammonia. — Ammonia  in  pyridine  is  readily  detected 
by  means  of  phenolphthalein  or  litmus  paper,  on  which  the  pyridine  has 
no  action. 

Small  quantities  of  ammonia  are  best  tested  for  by  means  of  Nessler's 
reagent  (see  Potable  Waters),  5  c.c.  of  the  latter  being  added  to  10  c.c.  of 
a  i%  solution  of  the  pyridine  :  if  no  ammonia  is  present,  only  a  white 
precipitate  is  formed. 

4.  Distillation. — 100    c.c.    are    distilled  from    a   flask  of  glass  or,  in 
industrial  practice,   of  copper  of    about   200  c.c.   capacity  and  with  a 
short  neck  into  which  is  inserted  a  bulb  rectifier  of  the  dimensions  shown 
in  Fig.  39,  this  being  joined  to  a  condenser  at  least  40  cm.  long  and  fitted 


PYRIDINE 


333 


with  a  thermometer  with  its  bulb  central.  The  flask  is  heated  over  the 
aperture  in  an  asbestos  card  in  such  a  manner  that  5  c.c.  distil  per  minute  ; 
when  the  temperature  reaches  140°,  the  heating  is  interrupted,  the  liquid 
that  comes  over  being  still  collected  and  the  „,-*. 

volume  of  the  distillate  measured.  The  distilla- 
tion is  then  continued  up  to  160°  and  the 
volume  of  the  distillate  measured. 

5.  Behaviour  towards  Water.— 50  c.c.  of 
the  pyridine  are  treated  with  100  c.c.  of  water 
to  ascertain  if  the  two  liquids  mix  completely 
and  if  the   solution   is   clear  or  more  or  less 
opalescent.     The  opacity  may  be   determined 
best  by  looking  through  the  mixture  in  a  tube 
such    as    is    indicated   under    i    (above)    and 
determining    the    possibility    or   otherwise  of 
reading  print  of  definite  dimensions. 

6.  Behaviour  towards  Caustic  Soda. — In  a  graduated  cylinder  with 
a  ground  stopper,  20  c.c.  of  the  pyridine  are  shaken  with  20  c.c.  of  caustic 
soda  solution,  D  1-4  (50  grams  of  sodium  hydroxide  in  100  c.c.)  and  left 
for  an  hour  ;  the  volume  of  the  upper  layer,  consisting  of  the  pyridine  bases, 
is  then  read.     The  difference  between  this  volume  and  20  c.c.  gives  the 
water  content. 

7.  Determination  of  the  Bases. — 10  c.c.  of  the  pyridine  are  diluted 
with  water  to  100  c.c.  and  10  c.c.  of  this  solution  titrated  with  normal  sul- 
phuric acid  until  a  drop  of  the  liquid  produces  on  Congo  red  paper  x  a  blue 
ring,  which  quickly  disappears.     The  result  is  expressed  by  indicating  the 
number  of  c.c.  of  normal  acid  employed. 

A  more  exact  determination  is  obtained  by  Franyois'  gravimetric 
method,2  based  on  the  insolubility  in  anhydrous  ether  of  the  additive  com- 
pound of  pyridine  hydrochloride  with  gold  chloride.  About  o-i  gram  of 
the  material  is  weighed  into  a  porcelain  basin  and  treated  with  water,  20—30 
drops  of  hydrochloric  acid  and  excess  of  gold  chloride  solution,  a  precipitate 
being  formed  and  the  liquid  remaining  deep  yellow.  The  whole  is  evaporated 
to  dryness  on  a  water-bath  and,  when  all  the  hydrochloric  acid  is  eliminated, 
washed  by  decantation  with  anhydrous  ether  as  long  as  any  colour  is  still 
removed  (to  eliminate  the  excess  of  gold  chloride).  The  precipitate  remain- 
ing in  the  dish  is  calcined  and  the  metallic  gold  weighed  :  Au  x  0-401  — 
pyridine,  when  pure  pyridine  is  taken.  With  crude  pyridine,  the  weight 
of  the  gold  must  be  multiplied  by  the  coefficient  0-5583  (deduced  from 
the  mean  molecular  weight  of  the  bases,  no). 

*** 

The  requirements  for  pyridine  bases  to  be  used  for  denaturation  are  : 
Test  i  :   should  remain  colourless  or  less  coloured  than  the  solution  of  iodine 
indicated. 

1  Prepared  by  immersing  chemically  pure  filter- paper  in  i%  aqueous  Congo  red 
solution  and  allowing  to  dry. 

2  Comptes  rendus,  1903,  Vol.  137,  p.  329. 


334  PYRIDINE 

Test  2  :  the  weight  of  the  precipitate  obtained  with  cadmium  chloride  should 
not  be  less  than  0-025  gram. 

Test  3  :    ammonia  absent. 

Test  4  :  at  least  50  c.c.  should  distil  below  140°  and  not  less  than  90  c.c. 
below  1 60°  (including  the  preceding  amount). 

Test  5  :  should  mix  completely  with  water  and  give  a  clear  or  barely  opales- 
cent solution. 

Test  6  :  the  layer  of  pyridine  bases  separating  should  occupy  at  least  18-5  c.c. 

Test  7  :   not  less  than  9-5  c.c.  N-sulphuric  acid  should  be  used. 


CHAPTER  VIII 

MINERAL    OILS 
AND  PRODUCTS  DERIVED  FROM  THEM 

Crude  petroleum  yields  various  industrial  products  which  may  be  grouped 
in  the  following  classes  : 

1.  Light  oils  (gasoline  and  naphtha),  b.pt.  below  150°  C. 

2.  Lamp  oil  or  kerosene,  principally  the  fractions  boiling  between  150° 
and  310°. 

3.  Medium  oils  (gas  oils),  intermediate  to  lamp  oil  and  the  heavy  oils. 

4.  Heavy  oils,  which  include  the  fractions  distilling  above  300—310° 
and  treated  to  render  them  suitable  as  lubricants. 

5.  Residuum,  which  consists  of  the  residue  left  after  distillation  of  the 
light  and  medium  oils  and  sometimes  also  of  part  of  the  heavy  oils,  without 
further  treatment. 

6.  Vaseline,  composed  of  hydrocarbons  semi-solid  at  the  ordinary  tem- 
perature. 

7.  Solid  paraffin  or  paraffin  wax,  formed  of  solid  hydrocarbons. 
Products  analogous  to  these  are  obtained  by  distillation  of  bituminous 

shales  and  are  termed  shale  oils  ;  these  also  yield  light  oils  (shale  spirit), 
burning  oils,  heavy  oils,  and  a  considerable  quantity  of  solid  paraffin. 

Similar  to  the  last  is  ceresine,  obtained  by  refining  ozokerite  or  earth 
wax.  A  product  of  similar  appearance  to  ozokerite  is  montan  wax. 

These  products  are  treated  in  the  following  articles,  together  with  lubri- 
cants, now  largely  used  industrially  and  mostly  having  a  basis  of  mineral  oil. 

In  sampling  these  products,  reference  may  be  made  to  the  directions 
given  for  tar. 

CRUDE  PETROLEUM 

This  is  usually  a  brown  or  blackish  liquid,  but  sometimes  reddish  or 
yellow,  with  a  characteristic  bituminous  odour  ;  it  is  often  turbid  owing 
to  the  presence  of  suspended  water  and  solid  substances. 

The  tests  to  be  made  are  partly  physical  and  partly  chemical. 

1.  Physical  Examination 

1.  Determination  of  the  Specific  Gravity. — The  hydrometer  or  the 
Westphal  balance  is  used,  or,  if  the  amount  of  substance  available  is  small 

335 


336 


CRUDE  PETROLEUM 


or  if  very  exact  results  are  required,  the  picnometer.  The  determination 
should  be  made  at  15°  or  referred  to  15°,  the  mean  temperature  coefficient 
of  specific  gravity  being  0-0007  (0-0006—0-0008)  per  i°. 

2.  Fractional  Distillation. — In  order  that  concordant  results  may 
be  obtained,  this  should  always  be  carried  out  under  certain  definite  con- 
ditions and  in  an  apparatus  of  fixed  dimensions.  Engler's  flask,  shown 
in  Fig.  40,  is  generally  used.  100  c.c.  of  the  oil  are  placed  in  the  flask, 
which  is  connected  with  a  condenser  60  cm.  long  and  heated,  both  the  flame 
and  the  flask  being  protected  with  a  sheet  metal  mantle. 

The  initial  temperature  of  distillation  is  that  at  which  the  first  drop 
of  distillate  issues  from  the  condenser  fitted  to  the  side-tube  of  the  flask. 
The  velocity  of  distillation  should  be  such  that  two  drops  pass  over  per 
second.  The  distillate  is  collected  in  several  graduated  cylinders,  or  in  a 
single  100  c.c.  cylinder  in  which  the  volumes  of  the  distillates  at  the  different 


e^m.-i.s 


FIG.  40 


FIG.  41 


temperatures  are  read  off  successively.  The  distillation  is  at  an  end  when 
the  flask  contains  only  residuum  or  white  fumes  appear.  The  fractions 
usually  collected  are  : 

Benzine  :    up  to  150°  C. 

Lamp  oil :    150-300°. 

Heavy  oils  :    above  300°. 

In  the  Italian  Customs  Laboratory,  for  the  determination  of  the  frac 
tions  distilling  below  310°  for  fiscal  purposes,  use  is  made  of  a  flask  similar 
to  the  preceding  but  of  the  dimensions  shown  in  Fig.  41.  100  c.c. 
of  the  petroleum  are  then  distilled,  the  flask  being  heated  over  a  gauze 
by  a  small  flame  ;  subsequently  the  flame  is  enlarged,  and  it  may  finally  be 
necessary  to  surround  the  flask  with  an  asbestos  mantle.  The  rate  of  dis- 


CRUDE  PETROLEUM  337 

tillation  should  be  such  that  about  2  grams  of  distillate  collect  per  minute. 
The  weight  of  the  distillate  up  to  310°  is  determined. 

If  the  mineral  oil  contains  much  water,  it  is  convenient  to  dehydrate 
it  by  means  of  calcium  chloride  and  to  decant  it  before  distillation  in  order 
to  avoid  bumping  during  the  heating. 

3.  Flash  Point. — The  flash  point  of  an  oil  is  the  temperature  correspond- 
ing with  the  initial  evolution  of  vapour  forming  with  air  a  mixture  capable 
of  exploding  in  contact  with  a  flame,  or,  more  accurately,  the  temperature 
at  which  such  vapour  can  be  detected  under  definite  experimental  con- 
ditions. 

This  determination  is  made  with  crude  petroleum  as  with  light  oils  (see 
later).  With  crude  petroleums  poor  in  light  oils,  however,  the  high  flash 
point  requires  the  use  of  the  apparatus  employed  with  lamp  oil  or  heavy 
oils  (see  the  paragraphs  concerned). 

4.  Temperature  of  Ignition. — This  is  the  temperature  at  which  the 
mineral  oil,  coming  into  contact  with  a  flame,  ignites  and  continues  to  burn. 
For  its  determination,  see  Light  Mineral  Oils. 

5.  Calorific  Power. — As  a  rule  this  is  determined  only  when  the  crude 
petroleum  is  to  be  used  as  a  fuel,  as  is  the  case  with  that  from  certain  localities 
(Texas,  California)  ;   the  Mahler  bomb  calorimeter  is  used  (see  Fuels).     If 
the  petroleum  is  poor  in  light  oils,  1-1-5  gram  of  it  is  weighed  directly  into 
the  capsule  for  holding  the  fuel,  but  if  rich  in  volatile  matter  it  is  well  to 
weigh  it  in  a  small  glass  bulb  with  the  ends  drawn  out,  the  igniting  wire 
being  passed  through  the  bulb  ;   the  bulb  is  placed  in  the  capsule  and  just 
before  the  bomb  is  closed  the  two  ends  are  broken  in  order  to  facilitate 
access  of  the  oxygen  to  the  liquid. 

2.  Chemical  Tests 

1.  Determination   of  the  Water    (Marcusson's  method).1 — 100    c.c. 
of  the  product  are  mixed  with  50  c.c.  of  xylene  and  the  mixture  distilled, 
in  presence  of  a  few  scraps  of  pumice,  best  in  an  oil-bath  until  the  water 
passes  over.     The  distillate  is  collected  in  a  graduated  cylinder    and   the 
volume  of  the  lower  aqueous  layer  measured. 

2.  Determination    of   the    Suspended    Solid    Matter. — The   oil   is 
shaken  with  at  least  20  times  its  volume  of  benzene  (to  dissolve  any  sus- 
pended pitch  and  asphalt),  filtered    after    standing  for  some  hours,  and 
the  residue  on  the  filter  washed  with  benzene,  dried  and  weighed. 

3.  Determination   of  the   Sulphur. — This  may  be  carried  out   by 
Eschka's  method  (see  Fuel)  or  in  the  Mahler  calorimetric  bomb.     With 
Eschka's  method,  i  gram  of  the  mineral  oil  is  mixed  with  sufficient  of  the 
mixture  of  magnesia  and  sodium  potassium  carbonate  to  give  a  dry  powder, 
which  is  covered  in  the  crucible  with  a  layer  of  the  mixture. 

In  the  bomb,  the  determination  is  made  simultaneously  with  that  of 
the  calorific  power,  the  sulphur  undergoing  conversion  to  sulphuric  acid. 

When  the  combustion  is  complete,  the  gas  formed  is  passed  through  about 
25  c.c.  of  8%  potassium  carbonate  solution,  the  apparatus  being  then  rinsed 
1  J.  Marcusson  :  Laboratoriumsbuch  fur  die  Industrie  der  Oele  und  Fetie  (1911). 

A.c.  22 


338 


CRUDE  PETROLEUM 


out  with  about  300  c.c.  of  water  in  all.  The  whole  is  then  evaporated  on 
a  water-bath  to  about  50  c.c.,  and  filtered,  the  filter  being  washed  with 
hot  water  ;  the  filtrate  is  acidified  with  hydrochloric  acid  and  the  sulphuric 
acid  precipitated  as  barium  sulphate  :  BaS04  x  0-1374  =  S. 

This  method  is  also  applicable  to  all  derivatives  of  crude  petroleum  and 
always  gives  good  results. 

4.  Determination  of  the  Solid  Paraffin. — This  is  effected  by  Holde's 
method,  after  fractions  below  300°  have  been  eliminated.     To  this  end, 
100  grams  of  the  crude  petroleum  are  rapidly  distilled,  the  distillate  up  to 
300°  being  collected.     If  the  residue  from  the  distillation  is  dark  and  turbid, 
as  is  usually  the  case,  it  also  should  be  distilled — the  thermometer  and 
condenser  having  been  removed — until  only  fixed,  carbonaceous  residue 
remains  in  the  retort.     The  distillate  above  300°  (or  the  oil  remaining  in 
the  flask  if  it  is  not  distilled)  is  weighed  and  treated  as  follows  in  the  appara- 
tus shown  in  Fig.  42. 

This  consists  of  a  vessel  surrounded  by  felt  and  containing  an  ice-salt 
mixture  in  which  are  immersed  the  tubes  containing 
the  test  material  and  the  funnel  used  for  the  filtration  ; 
the  funnel  is  connected  with  a  pump  flask.  The  ap- 
paratus is  provided  with  another  tube  (5)  by  means  of 
which  the  water  from  the  freezing  mixture  may  be 
run  off. 

Of  the  oil  distilled  as  described  above,  5—10  grams 
are  placed  in  a  wide  test-tube  and  dissolved  in  the 
necessary  quantity  of  a  mixture  in  equal  proportions 
of  absolute  alcohol  and  ether.  The  tube  is  placed  in  the 
freezing  mixture  so  as  to  keep  it  at  about  —  20°,  and, 
while  the  liquid  is  stirred  with  the  thermometer,  the 
alcohol-ether  mixture  added  until  the  oily  drops  which 
separate  are  redissolved  and  only  the  solid  paraffin 
remains  out  of  solution.  The  liquid  is  then  filtered  by 
means  of  a  pump  on  the  funnel  kept  between  — 15° 
and  —  20°,  the  residue  being  washed  with  cooled 
alcohol-ether  mixture  (if  the  solid  paraffin  is  soft,  it  is  well  to  wash  with 
a  mixture  of  2  parts  of  alcohol  and  one  of  ether)  until  a  few  c.c.  of  the  washing 
liquid  leave  no  appreciable  oily  residue  on  evaporation.  The  remaining 
solid  paraffin  is  then  dissolved  on  the  filter  in  hot  benzene  into  a  tared  glass 
dish,  the  benzene  being  evaporated  on  a  water-bath — which  finally  should 
boil  vigorously — and  the  dish  dried  for  15  minutes  at  105°,  cooled  in  a 
desiccator  and  weighed.  The  percentage  of  solid  paraffin  in  the  original 
oil  is  then  calculated. 

By  this  method,  a  small  quantity  of  solid  paraffin  remains  dissolved  in 
the  alcohol-ether  mixture  ;  the  result  obtained  should,  therefore,  be  increased 
by  0-2%  for  a  very  fluid  oil,  or  by  0-4%  for  an  oil  so  rich  in  solid  paraffin 
that  it  deposits  it  at  15°. 

5.  Detection    and    Determination    of   the    Asphalt. — Usually    two 
varieties  of  asphalt  are  distinguished  in  crude  petroleums,  namely,  hard 
and  soft  asphalt. 


FIG.  42 


CRUDE  PETROLEUM  339 

1.  DETECTION,     (a)  Hard  asphalt.     About  0*3  gram  of  the  oil  is  shaken 
in  a  test-tube  with  20  c.c.  of  petroleum  ether  (D  not  above  07)  and  left 
overnight ;  any  hard  asphalt  present  is  deposited  in  blackish  flocks  soluble 
in  benzene. 

(b)  Soft  asphalt.  About  0-5  gram  of  the  oil  is  dissolved  in  a  test-tube 
in  15  c.c.  of  ether  and  the  liquid  treated  with  7-5  c.c.  of  96%  alcohol ;  any 
soft  asphalt  present  is  precipitated  in  the  form  of  flocks,  which  unite  to  a 
viscous  mass  adherent  to  the  walls  of  the  tube  and  soluble  in  benzene. 

2.  QUANTITATIVE  DETERMINATION,     (a)  Hard  asphalt.     About  5  grams 
(or  more,  with  a  product  poor  in  asphalt)  of  the  oil  are  shaken  in  a  litre  flask 
with  200  c.c.  of  the  petroleum  ether  used  for  the  qualitative  test  and  left 
at  rest  for  a  day.     The  liquid  is  then  decanted  on  to  a  pleated  filter,  to 
which  also  the  insoluble  substances  are  transferred,  flask  and  filter  being 
washed  with  benzine  until  a  few  drops  of  the  filtrate  leave  no  oily  residue 
on  evaporation.     The  insoluble  residue  on  the  filter  is  at  once  dissolved  in 
hot  benzene,  the  solvent  evaporated  in  a  tared  dish  and  the  residue  dried 
at  105°  and,  when  cold,  weighed. 

(b)  Soft  asphalt.  5  grams  of  the  product  are  dissolved,  in  a  bottle 
fitted  with  a  ground  stopper  and  of  about  300  c.c.  capacity,  in  25  volumes 
of  ether,  12-5  volumes  of  96%  alcohol  being  run  in  to  the  solution,  drop  by 
drop  and  with  shaking,  from  a  burette.  After  standing  for  5  hours  at  15°, 
the  liquid  is  filtered  and  the  bottle  and  filter  washed  with  the  alcohol-ether 
mixture  (1:2)  until  the  washing  liquid  leaves  no  oily  residue,  or  at  most 
traces  of  pitchy  substances,  on  evaporation. 

The  precipitate,  which  may  contain  solid  paraffin  as  well  as  asphalt, 
is  dissolved  in  benzene,  the  solution  evaporated,  the  residue  treated  re- 
peatedly in  the  hot  with  96%  alcohol  (about  30  c.c.)  until  the  alcoholic 
extracts  no  longer  deposit  solid  paraffin  on  cooling.  The  residue,  consisting 
only  of  the  soft  asphalt,  is  dried  for  15  minutes  at  105°  and  weighed. 

For  precipitating  the  asphalt  in  mineral  oils,  besides  benzine  and  alcohol- 
ether,  also  butanone,1  amyl  alcohol  and  ethyl  acetate  have  been  proposed. 

Different  solvents  precipitate  asphaltic  substances  in  different  quantities 
and  of  different  qualities,  so  that  the  analytical  results  are  only  relative  and 
not  absolute. 

6.  Behaviour  towards  Concentrated  Sulphuric  Acid. — Concen- 
trated sulphuric  acid  precipitates  from  crude  petroleum  asphaltic  and 
pitchy  substances  in  larger  or  smaller  quantity.  In  many  cases  it  is,  there- 
fore, useful  to  determine  these  substances,  this  being  done  in  the  following 
manner. 

In  a  graduated  cylinder  with  a  ground  stopper  20  c.c.  of  the  oil  are 
dissolved  in  80  c.c.  of  petroleum  ether  (D  0-700,  and  ascertained  by  pre- 
liminary trial  to  be  unattacked  by  cone,  sulphuric  acid),  the  solution  obtained 
being  shaken  for  a.  minute  with  10  c.c.  of  cone,  sulphuric  acid  (66°  Baume) 
and  left  until  the  liquid  separates  sharply  into  two  layers.  From  the 
volume  of  the  dense,  black,  lower  layer  is  subtracted  the  volume  of  acid 
added  (10  c.c.),  the  difference  representing  the  quantity  of  asphalt  and 
pitchy  substances  in  20  c.c.  of  the  oil. 

1  Schwarz  :    Chem.  Zeit.,  1911,  35,  p,  1417. 


340  LIGHT  MINERAL  OILS   (BENZINE) 

Crude  petroleums  have  specific  gravities  varying  from  0-771  to  about  1-020, 
the  Russian  being  usually  denser  than  the  American. 

As  regards  fractional  distillation,  good  American  crude  petroleums  generally 
contain  much  light  oil  and  lamp  oil,  while  their  heavy  fractions  contain  marked 
quantities  of  solid  paraffin.  Russian  petroleums,  however,  furnish  less  quan- 
tities of  light  and  middle  distillates,  whilst  the  heavy  fractions  abound,  although 
these  are  poor  in  paraffin  wax.  Galician  and  Rumanian  petroleums  are  mostly 
rich  in  middle  fractions,  and  their  heavy  ones  contain  solid  paraffin.  Italian 
petroleums  are  usually  richer  in  light  and  middle  than  in  heavy  fractions. 

The  flash  point  is  mostly  near  o°,  but  varies  with  the  content  of  light  oils. 

The  sulphur  content  is  generally  low  (less  than  i%),  but  in  some  cases,  e.g., 
in  Texan  and  Californian  petroleums,  more  is  found  (4-5%). 

The  calorific  power  of  crude  petroleums  is  as  a  rule  10,000-11,000  cals.  and 
diminishes  as  the  specific  gravity  increases.  Petroleums  poor  in  the  lighter 
fractions  are  more  particularly  used  directly  as  fuels,  e.g.,  those  of  Texas,  Cali- 
fornia and  Mexico  ;  petroleums  with  little  sulphur  are  preferable  for  this  pur- 
pose, but  those  with  larger  proportions  may  also  be  used. 


LIGHT    MINERAL    OILS 
(Benzine) 

These  are  volatile,  mobile,  colourless,  or  pale  yellow  liquids,  usually 
clear  but  sometimes  opalescent,  in  which  case  the  presence  of  water  is  to 
be  suspected. 

The  following  tests  and  determinations  are  made  : 

1.  Determination  of  the   Specific   Gravity. — This  is  made  at  15° 
by  the  methods  indicated  for  crude  petroleum. 

For  fiscal  purposes  the  Italian  Customs  authorities  use  two  thermo- 
aerometers,  one  for  the  densities  0-610-0-700  and  the  other  for  0-680-0-770. 
By  means  of  tables  published  on  the  authority  of  the  Ministry  of  Finance,1 
density  readings  made  at  other  temperatures  are  reduced  to  15°.  If  the 
weight  of  any  consignment  is  known,  the  volume  can  then  be  calculated. 

Besides  as  a  means  of  characterising  the  various  products  comprised  under 
the  name  light  petroleum  oils,  the  specific  gravity  may  serve  as  an  indication 
of  the  presence  of  benzoles,  oil  of  turpentine  or  light  resin  oils,  all  of  these  having 
much  higher  specific  gravities — 0-86  or  more. 

2.  Distillation.— Use  is  made  of  the  flask  already  described  for  crude 
petroleum,  this  being  connected  with  a  good  condenser  and  heated  on  a 
sand-bath  with  a  lamp  the  flame  of  which  is  completely  enclosed  in  a  wire 
gauze  cage,  so  that  ignition  of  the  vapours  in  case  the  flask  breaks  may 
be  avoided. 

The  temperature  at  which  the  distillation  commences  is  noted  and  the 
distillate  collected  either  in  a  graduated  cylinder,  the  volume  for  each  10° 
being  observed,  or  in  a  separate  tared  vessel  for  each  fraction,  the  vessel 
being  afterwards  reweighed.  If  the  whole  of  the  liquid  does  not  distil 
over  below  150°,  the  distillation  is  stopped  at  this  temperature  and  the 
residue  in  the  flask  weighed. 

1  Tables  for  the  determination  of  the  density  and  volume  at  15°  of  mineral  oils, 
Rome,  1912. 


LIGHT  MINERAL  OILS   (BENZINE)  341 

When  a  more  thorough  separation  of  the  different  fractions  is  desired, 
a  flask  surmounted  by  a  dephlegmator  may  be  used. 

With  very  light,  rectified  oils,  it  is  useful  to  evaporate  a  portion  on  the 
water- bath  to  ascertain  if  any  residue  remains,  or  to  allow  a  little  to  evaporate 
spontaneously  on  a  filter-paper  to  see  if  any  oily  spot  is  left. 

Where  exact  results  are  required,  allowance  must  be  made  for  the  atmospheric 
pressure  when  this  varies  by  as  much  as  +  5  mm.  from  the  normal  (760  mm.). 

3.  Flash  Point. — For  this  purpose  use  is  made  of  the  inner  vessel  A 
of^the  Abel  apparatus  (see  Lamp  Oil,  Physical  Tests,  4),  this  being  placed 
in  a  metal  vessel  about  6  cm.  high  and  9  cm.  in  diameter  containing  alcohol ; 
this  vessel,  in  its  turn,  is  placed  in  a  larger  metal  vessel,  also  containing 
alcohol  and  surrounded  with  felt.     Solid  carbon  dioxide  is  introduced  into 
the  alcohol  until  the  temperature  in  the  liquid  to  be  examined  reaches 
—  50°  or  —  60°  *    the  temperature  is  then  allowed  to  rise  slowly  and  the 
observations  begun  as  with  lamp  oil. 

This  determination  is  seldom,  made,  as  it  is  known  that  naphtha  has  a  low 
flash  point,  which  is  generally  far  below  o°,  although  with  some  of  the  heavier 
types  it  may  be  slightly  above  o°. 

4.  Temperature  of  Ignition. — After  the  flash  point  has  been  deter- 
mined, the  cover  of  the  vessel  A  is  removed  and  for  every  0-5°  rise  of  tem- 
perature a  flame  is  brought  near  to  the  surface  of  the  liquid.     The  tem- 
perature of  ignition  is  taken  as  that  at  which  persistent  combustion  of  the 
liquid  itself  takes  place. 

This  determination  also  is  rarely  made  for  the  reasons  indicated  above, 
the  temperature  of  ignition  being  only  a  few  degrees  (3  or  4)  above  the  flash 
point. 

5.  Degree  of  Refining. — The  extent  of  rectification  of  a  light  oil  is 
indicated  by  the  following  tests  : 

(a)  The  oil  is  shaken  with  an  equal  volume  of  cone,  sulphuric  acid  to 
ascertain  if  the  latter  appears  coloured  after  separation. 

(b)  The  oil  is  shaken  with  boiling  water  and  the  latter  subsequently 
tested'^with  litmus  and  with  barium  chloride. 

(c)  The  liquid  is  boiled  for  a  few  minutes  with  alcohol  containing  a 
few  drops  of  ammonia  and  then  treated  with  silver  nitrate  to  see  if  any 
brown  coloration  develops. 

6.  Detection  and  Determination  of  Benzoles. 

(i)  DETECTION,  (a)  According  to  Holde,  tar-pitch,  previously  washed 
with  petroleum  benzine  (D  070—0-71)  until  the  latter  dissolves  no  more, 
is  shaken  with  the  light  oil  under  examination.  The  latter  becomes  yellow 
or  brown  if  tar  benzoles  are  present. 

Not  less  than  5-10%  of  benzoles  are  detectable  in  this  way. 

(b)  5  c.c.  of  the  oil,  in  a  flask  fitted  with  a  reflux  condenser  and 
immersed  in  a  beaker  of  water,  are  treated  with  small  quantities  of  fuming 
nitric  acid  until  evolution  of  red  vapours  ceases  (20  c.c.  of  acid  usually 
suffice).  At  the  end  of  the  reaction,  the  contents  of  the  flask  are  poured 
into  a  graduated  100  c.c.  cylinder  containing  60%  alcohol.  The  flask  is 


342 


LIGHT  MINERAL  OILS   (BENZINE) 


washed  out  with  alcohol  of  the  same  concentration,  this  being  poured  into 
the  cylinder  and  the  volume  made  up  to  100  c.c.  and  the  whole  shaken. 
Any  nitro-derivatives  formed  from  benzoles  present  pass  into  solution  in 
the  alcohol,  while  the  mineral  oil  remains  undissolved ;  if  the  volume  of 
the  latter  has  been  diminished  by  5  c.c.,  it  is  concluded  that  the  oil  contained 
benzoles. 

This  procedure  is  valid  only  for  light  oils  composed  of  paraffin  hydrocarbons, 
which  are  not  attacked  by  nitric  acid. 

2.  QUANTITATIVE  DETERMINATION.  This  is  effected  by  Kramer  and 
Bottcher's  method,  which  is  based  on  the  absorption  of  aromatic  hydro- 
carbons by  sulphuric  acid  of  D  1-84  at  15°,  this  being  prepared  from  80 
parts  of  cone,  acid  and  20  parts  of  fuming  acid.  In  a  flask  holding  about 
75  c.c.,  surmounted  by  a  long  neck  graduated  in  o-i  c.c.  for  50  c.c.,  25  c.c. 
of  the  oil  are  shaken  for  15  minutes  with  25  c.c.  of  the  above  sulphuric 
acid.  After  a  rest  of  30  minutes,  concentrated  sulphuric  acid  is  poured 
into  the  flask  until  the  layer  of  benzine  is  entirely  in  the  graduated  neck, 
the  volume  of  this  being  read  off  after  the  lapse  of  an  hour.  The  difference 
between  this  volume  and  the  original  one  represents  the  aromatic  hydro- 
carbons. 

7.  Oil  of  Turpentine. — The  procedure  followed  is  that  indicated  for 
the  detection  of  mineral  oils  in  oil  of  turpentine  (see  Chapter  on  Turpentine 
and  its  Products  :  Oil  of  Turpentine,  9,  in  Vol.  II). 


* 
*  * 


Crude  light  oils  are  usually  yellowish  and  often  contain  a  certain  quantity 
of  less  volatile  oils,  but  the  rectified  products  should  be  colourless  and  should 
give  negative  results  with  the  tests  described  under  5  (above). 

Rectified  light  oils  are  subdivided,  according  to  the  temperature  at  which 
they  distil,  into  different  products,  named  differently  in  various  countries. 
Usually  the  following  products  are  distinguished  : 


Name. 

Specific 
Gravity. 

Temperature 
of 
Distillation. 

Light  petroleum  ether  (Gasoline  I)        
Heavy  petroleum  ether  (Gasoline  II,  Light  benzine)  . 
Benzine  for  pleasure  automobiles    ~)                  ... 
Benzine  for  ordinary  automobiles    [•  Petrols     . 
Benzine  for  heavy  automobiles        j                  ... 
Benzine  properly  so-called  (Naphtha  C) 
Ligroin  (Naphtha  B)         

0-620-0-660 
0-660-0-680 
0-680-0-705 
0-690-0-725 
0-720-0-770 
0-670-0-720 
O-7O7—O-7^O 

30-80° 

30-95° 
60-100° 
60-120° 
60-150° 
60-100° 
80-120° 

Cleaning  oil  Naphtha  (Naphtha  A)       

0-720—0-7^0 

120—150° 

Substitute  for  oil  of  turpentine  

O-73O—  O-7SO 

110—150° 

The  limits  indicated  for  the  boiling  points  of  petrols  are  not  always  alone 
to  be  taken  as  a  basis  for  judging  of  their  quality,  as  this  depends  essentially 
on  the  respective  proportions  of  the  various  fractions  distilling  between  such 
limits.  For  instance,  some  brands  of  benzine  distil  mainly  below  90° — -these 
being  the  best — while  with  others,  more  than  one-half  distils  above  90°,  these 
being  the  least  valuable. 

The  calorific  power  of  petrol  is  about  11,000-12,000  cals. 


LIGHTING  OILS 


343 


Paraffin  oil  or  kerosene,  used  for  lighting  purposes,  is  a  clear  mobile 
liquid,  sometimes  colourless,  but  usually  more  or  less  yellow  and  fluorescent 
and  of  characteristic  odour.  Physical  as  well  as  chemical  tests  are  made. 


1.  Physical  Tests 

1.  Colour. — The  colour  of  lamp  oil  may  be  used  as  a  basis  for  commer- 
cial contracts.  Its  intensity  is  determined  by  Stammer's  colorimeter  (Fig. 
43),  which  consists  of  two  vertical  brass  cylinders 
blackened  inside,  one  of  them,  closed  at  the  bottom  by 
a  glass,  being  charged  with  the  liquid  to  be  examined  ; 
in  the  other  cylinder  is  inserted  a  standard  glass 
coloured  with  uranium  oxide  to  a  definite  intensity, 
and  under  both  cylinders  is  a  white  reflecting  surface. 
By  means  of  two  prisms,  the  two  colours  to  be  com- 
pared are  observed  in  the  two  halves  of  the  circular 
field  of  the  eyepiece.  The  depth  of  the  liquid  may  be 
varied  by  vertical  displacement  of  the  system  of  prisms 
along  with  a  cylinder  closed  at  the  bottom  by  a  glass 
disc  and  dipping  into  the  cylinder  of  liquid.  When 
uniformity  of  the  field  has  been  attained  the  depth  of 
the  liquid  giving  a  colour  intensity  equal  to  that  of 
the  standard  glass  is  read  off  on  a  scale. 

The  four  grades  of  colour  usually  distinguished  in 
the  trade,  with  the  corresponding  depths  in  Stammer's 
colorimeter  are  : 


Standard  white. 
Prime  white 
Superfine  white 
Water  white 


50  mm. 
86-5  „ 

199    » 

310     ,,      or  more 


FIG.  43 


In  England  and  Russia,  use  is  largely  made  of  the  Wilson  colorimeter,1 
which  contains  four  standard  coloured  glasses  corresponding  with  the 
different  commercial  grades. 

2.  Determination  of  the  Specific  Gravity. — As  with  crude  petro- 
leums, at  15°. 

For  determining  the  density  of  lamp  oil  for  fiscal  purposes,  the  Italian 
Customs  authorities  use  a  thermo-aerometer  graduated  from  0-750-0-840, 
and  tables  of  temperature  corrections  have  been  prepared.2 

3.  Fractional  Distillation. — -As  with  crude  petroleum. 

4.  Flash  Point. — Many  forms  of  apparatus  have  been  devised  for  this 
purpose.     The  results  obtained  are  purely  conventional  and  vary  from 

1  Boverton  Redwood  :    Petroleum,  London,  1913. 

2  Tables  for  the  determination  of  the  density  and  volume  at  15°  of  mineral  oils, 
Rome,  1912. 


344 


LIGHTING  OILS 


one  form  of  apparatus  to  another,  so  that  comparable  data  are  obtainable 
only  with  one  and  the  same  instrument  under  identical  conditions. 

The  apparatus  used  officially  in  Italy  and  also  in  Great  Britain,  Germany 
and  Austria  is  that  of  Abel,  improved  by  Pensky  (Fig.  44).  The  oil  is 
placed  in  a  brass  cylinder  A ,  tinned  inside  and  furnished  with  a  gauge  index 
/.  Its  cover  carries  a  thermometer  t  with  a  scale  extending  from  10°  to 
50°  and  divided  into  half-degrees,  and  a  clockwork  mechanism  m  set  in 
motion  by  a  lever  a.  Pressure  of  the  latter  opens  automatically  a  small 
window  in  the  cover  and  at  the  same  time  lowers  a  small  flame  in  b  to  the 

aperture  and  then  raises  it  again, 
the  window  immediately  closing. 
The  entire  movement  should  occupy 
two  seconds. 

The  vessel  A  is  heated  by  a  water 
bath  B,  the  intermediate  space  C 
being  left  empty,  and  is  supported 
on  an  ebonite  ring  fixed  to  the  bath 
B.  The  latter  contains  a  thermo- 
meter T  with  a  red  mark  at  55°. 
The  bath  is  first  heated  to  this 
temperature,  the  covered  vessel  con- 
taining the  oil  up  to  the  prescribed 
level  being  fitted  and  the  ther- 
mometer t  in  the  oil  read.  For  each 
rise  of  temperature  of  0-5°  the  clock- 
work mechanism  is  operated,  the 
test  being  repeated  until  the  flame 
causes  a  small  explosion  :  the  tem- 
perature then  shown  is  the  flash 
point  and  should  be  corrected  for 
the  pressure  (+  0-035°  Per  *  r*1111- 
below  or  above  760  mm.),  the  result 
FIG.  44  being  returned  to  the  nearest  half- 

degree. 

The  dimensions  of  all  parts  of  the  apparatus  are  exactly  controlled 
and  with  careful  working  the  results  should  not  vary  by  more  than  0-5-1° 
at  the  most. 

5.  Temperature     of     Ignition. — When    the    flash    point    has    been 
measured,  the  cover  of  the  vessel  A  is  removed  and  a  thermometer  sup- 
ported in  the  oil,  the  heating  being  continued  and,  after  each  i°  rise,  a 
flame  brought  near  the  surface  of  the  liquid  without  touching  it.     When 
the  oil  fires,  the  temperature  is  observed,  the  thermometer  immediately 
withdrawn  and  the  oil  extinguished  with  an  asbestos  card. 

6.  Determination  of  the  Viscosity. — -This  is  not  usually  carried  out 
with  illuminating  oil,  but  it  may,  if  required,  be  effected  as  in  heavy  oils 
(q.v.,  Physical  Tests,  7)   or,   more  exactly,   by  means  of  the  Ubbelohde 
viscometer.1 

1  Petroleum,  1909,  IV,  p.  861. 


LIGHTING  OILS 


345 


7.  Determination  of  the  Illuminating  Power. — This  requires  a 
-photometer,  one  of  those  most  largely^used  being  that  of  Lummer  and  Brod- 
hun  (Fig.  45),  which  is  an  improved  form  of  the  Bunsen  type.  It  consists 


FIG.  45. 

of  a  closed  chamber  with  two  opposite  circular  apertures,  by  means  of 
which  the  two  faces  of  a  white  screen  in  the  chamber  are  illuminated  respec- 
tively by  the  lamp  to  be  examined  and  by  a  lamp  chosen  as  unit.  The  two 
faces  of  the  screen  reflect  the  light,  by  means  of  a  system  of  lenses,  on  to 
two  concentric  zones  of  the  field  of  the  telescope 
eye-piece  shown  to  the  left  of  the  figure.  When 
the  screen  is  equally  illuminated  on  both  faces,  the 
two  zones  of  the  field  appear  exactly  similar.  The 
two  sources  of  light  are  placed  at  the  extremities  of  a 
double  guide  3  metres  in  length  and  graduated  in 
half-centimetres — the  photometric  bench.  The  position 
of  the  photometer  is  adjusted  between  the  lights  so 
that  the  field  is  uniformly  illuminated  :  the  inten- 
sities of  the  two  lights  are  then  proportional  to  the 
squares  of  their  respective  distances  from  the  screen 
of  the  photometer. 

Photometric  observations  are  made  in  a  dark  room  with  blackened 
walls,  with  a  temperature  about  constant  and  no  sensible  air  currents.  The 
standard  lamp  used  is  the  Hefner  amyl  acetate  lamp  with  a  flame  4  cm. 
high  (Fig.  46). 

The  values  obtained  with  other  types  of  lamp  still  in  use  in  different  countries 
may  be  converted  into  those  given  by  the  Hefner  lamp  by  means  of  the  factors 
given  in  the  following  table  1  : 


FIG.  46. 


Uppenborn  and  Monasch  :  Lehrbuch  der  Photometric,  Munich  and  Berlin,  1 912. 


346 


LIGHTING  OILS 


TABLE    XLI 


International  Candle, 

Unit. 

Hefner 
Candle. 

Decimal  Candle  (Normal 
Candle),  American  Candle, 

Carcel. 

Pentane  Candle. 

Hefner  candle     .... 

I 

0-9 

0-093 

International   candle,  deci- 

mal candle  (normal  candle, 

American  candle,  pentane 

candle  

I'll 

I 

0-1035 

Carcel       

10-7^ 

Q'6^ 

I 

The  petroleum  to  be  tested  is  poured  into  a  lamp  and  the  latter  weighed, 
centred  on  the  photometric  bench  and  lighted,  the  time  being  noted.  The 
flame  is  kept  low  at  first  and  is  then  gradually  raised  until  it  is  as  large  as 
possible  without  smoking  and  without  the  wick  charring  excessively.  Photo- 
metric observations  are  then  begun  and  are  repeated  at  regular  intervals 
— the  time  of  each  being  noted — until  the  oil  is  almost  exhausted,  the  wick 
not  being  further  moved  ;  the  lamp  is  finally  extinguished  and  weighed, 
the  consumption  of  oil  being  thus  ascertained. 

The  position  of  the  Hefner  lamp  is  taken  as  the  zero  of  the  scale  and 
that  of  the  oil  lamp  as  300  cm.  ;  the  illuminating  power  of  the  lamp  is  then 
given  by  the  formula, 


=  (L  £Y 


i 


where  i  is  the  intensity  required,  expressed  in  candles  (Hefner),  /  the 
length  of  the  photometric  bench  and  x  the  distance  of  the  photometer 
screen  from  the  zero  point  of  the  scale.  The  mean  of  the  different  obser- 
vations gives  the  mean  intensity  in  candles. 

The  mean  consumption  per  candle-hour  is  the  quotient  of  the  total 
weight  of  oil  used  by  the  total  candle-hours,  and  the  yield,  that  is  the 
amount  of  light  (in  candle-hours)  produced  per  gram  of  oil,  the  quotient 
of  the  total  candle-hours  by  the  weight  of  oil  consumed. 

It  is  necessary  also  to  take  account  of  the  variation  of  the  luminous 
intensity  during  the  experiment.  As  a  rule,  after  reaching  its  maximum 
a  few  minutes  subsequent  to  the  lighting  of  the  lamp,  it  diminishes  more 
or  less  slowly  to  the  end,  mainly  on  account  of  the  carbon  ring  formed  at 
the  summit  of  the  wick  in  consequence  of  the  incomplete  combustion  of 
the  heavier  fractions,  this  hindering  the  rise  of  the  oil  into  the  flame.  This 
decrease  is  expressed  by  a  fraction,  the  numerator  of  which  is  the  difference 
between  the  maximal  luminous  intensity  reached  soon  after  the  beginning 
and  that  observed  just  before  the  exhaustion  of  the  oil,  and  the  numerator 
the  maximal  intensity. 


LIGHTING  OILS  347 

EXAMPLE  :    During  5  hours  the  following  intensities  were  observed,  the 
consumption  of  oil  being  180  grams. 

Luminous  intensity  in 

Time.  candles, 

ist  hour          .          .          .          .          .          .                     .  ;    9-50 

2nd     ,,            .          .          .          .          .          ...  9-00 

3rd      , 8-50 

4th      ,, 8-00 

5th      „ 7-50 


Total  candles     42-50 

Mean  luminous  intensity  =  42-50  :  5  =  8-50  candles. 

Mean  consumption  per  candle-hour  =  180  :  42-50  =  4-23  grams. 

Yield,  or  light  produced  per  gram  of  oil  =  42-50  :  180  =  0-23  candle-hour. 

Decrease  of  luminous  intensity  =  (9-50-7-50)  :  9-50  =  0-21. 

It  must  be  pointed  out  that  petroleums  of  different  quality  do  not  burn 
equally  well  in  all  lamps,  principally  on  account  of  the  different  quantities  of 
air  they  require  to  burn  completely.  If  the  lamp  does  not  allow  access  of 
sufficient  air  the  combustion,  being  incomplete,  will  give  rise  to  smoke  and 
unpleasant  smell,  whereas  excess  of  air  in  the  flame  will  cool  the  latter  too  much 
and  diminish  the  luminosity  as  well  as  the  consumption.  In  general,  Russian  oils 
require  more  air  than  the  American,  while  with  oils  from  the  same  locality, 
more  air  is  required  by  those  rich  in  heavy  and  poor  in  light  fractions.  In  any 
case  it  is  necessary,  to  obtain  comparable  results,  to  work  with  the  same  lamps 
and  to  allow  for  the  form  and  dimensions  of  their  essential  parts,  namely,  the 
holder,  burner  and  chimney.  Marked  influence  on  the  course  of  the  combus- 
tion is  also  exercised  by  the  wick,  especially  the  length  and  quality  of  the  fibre 
and  the  structure  and  compactness  of  the  tissue  ;  wicks  of  the  same  quality 
and  dimensions  should  be  used  in  all  measurements,  and  they  should  be  either 
new  or  washed  thoroughly  with  petroleum  ether  and  then  dried. 

8.  Behaviour  at  Low  Temperature. — This  test  is  made  on  oils  to 
be  used  in  the  open  in  cold  places.  A  little  of  the  oil  is  cooled  for  an  hour, 
in  a  test-tube  with  a  thermometer  passing  through  its  stopper,  at  the  lowest 
temperature  to  which  it  is  likely  the  oil  may  be  exposed,  to  ascertain  if 
the  oil  remains  clear  and  mobile  or  if  solid  substances  separate.  For  the 
procedure,  see  Heavy  Oils,  Physical  Tests,  8. 

2.  Chemical  Tests 

1.  Acidity. — This  may  be  due  to  inorganic  acids  (principally  sulphuric 
acid)  or  to  organic  acids.     The  tests  are  made  as  follows  : 

(a)  INORGANIC  ACIDS.     The  oil  is  shaken  with  tepid  water  containing 
a  little  methyl  orange  ;   if  the  colour  changes  to  red,  the  aqueous  layer  is 
separated  and  tested  with  barium  chloride. 

(b)  ORGANIC  ACIDS.     If  test  (a)  gives  a  positive  result,  the  oil  to  be 
used  for  the  present  test  is  first  washed  with  hot  water  :   100  c.c.   of 
the  oil  are  dissolved  in  100  c.c.  of  a  neutral  alcohol-ether  (i  :  4)  mixture 
in  presence  of  a  drop  of  phenolphthalein  solution  and  a  drop  of  N/io-sodium 
hydroxide  solution,  the  whole  being  shaken  in  a  cylinder :   the  red  colour 
persists  if  the  oil  is  neutral,  but  disappears  if  organic  acids  are  present. 

2.  Degree  of  Refining. — The  oil  is  shaken  with  an  equal  volume  of 


348  LIGHTING  OILS 

sulphuric  acid  (D  1-53)  and  note  made  if  the  latter  becomes  yellow  or  brown. 
If  any  appreciable  coloration  occurs,  it  is  desirable  to  ascertain  if  any  marked 
rise  of  temperature  takes  place. 

3.  Determination  of  the  Sulphur. — This  is  usually  done  only  with 
oils  having  a  penetrating  and  unpleasant  odour.     The  simplest  method  is 
that  of  Heussler  and  Engler,1   this  consisting  in  burning  the  petroleum  in 
a  suitable  lamp,  the  chimney  of  which  is  joined  to  a  bent  tube  dipping  into 
20  c.c.  of  5%  potassium  hydroxide  solution  made  just  yellow  by  bromine 
and  then  left  in  the  air  to  decolorise  ;   the  absorption  vessel  communicates 
with  a  pump.      The  lamp  charged  with  the  oil  is  weighed  and  lighted,  the 
tube  fitted  and  the  suction  adjusted  so  that  the  combustion  is  complete  and 
regular.     The  sulphurous  anhydride  produced  is  absorbed  and  transformed 
into  sulphuric  acid  by  the  alkaline  bromine  solution.     After  10-12  grams 
of  the  oil  are  burnt,  the  flame  is  extinguished,  a  little  more  air  drawn  through, 
the  lamp  again  weighed  and  the  sulphuric  acid  determined  as  barium  sul- 
phate.    The  caustic  potash  used  and  also  the  air  must,  of  course,  be  free 
from  sulphur  products. 

The  sulphur  may  also  be  determined  by  the  Mahler  calorimetric  bomb  (see 
Crude  Petroleum,  Chemical  Tests,  3). 

4.  Distinction  between  Petroleums  from  Different  Localities. — 

This  is  based  mainly  on  the  following  tests  : 

(a)  SPECIFIC  GRAVITY.    This  is  usually  0-780-0-805  for  American  and 
0-820—0-825  for  Russian  lighting  oils. 

A  better  criterion  than  the  specific  gravity  is  furnished  by  the  specific  gravities 
of  the  fractions  obtained  on  distillation,  these  differing  by  about  0-04  for  identical 
boiling  points.  Thus,  the  fractions  of  an  American  and  a  Russian  petroleum 
distilling  between  230°  and  250°  have  the  respective  densities  0-798  and  0-841, 
and  the  fractions  between  250°  and  270°  the  densities  0-809  and  0-850. 

(b)  TREATMENT  WITH  BROMINE.     2  or  3   c.c.  of  American  petroleum 
are  not  coloured  when  treated  with  a  drop  of  bromine,  whereas  other 
petroleums  become  coloured  under  these  conditions. 

(c)  SOLUBILITY  IN  A  MIXTURE  OF  CHLOROFORM  AND  ALCOHOL.    Riche 
and  Halphen  2  have  suggested  a  method  based  on  the  different  solubilities, 
in  a  mixture  of  chloroform  and  aqueous  alcohol,  of  fractions  of  equal  specific 
gravities  from  American  and  Russian  petroleums.     It  is  carried  out  as 
follows  :   Several  successive  fractions  of  the  oil  are  separated  by  distillation 
and  the  specific  gravity  of  each  of  them  determined  at  15°.     The  volume 
of  a  mixture  in  equal  volumes  of  pure  anhydrous  chloroform  and  92-8% 
alcohol  necessary,  when  run  in  slowly  from  a  burette  with  continual  shaking, 
to  remove  the  turbidity  produced,  is  then  determined.     For  the  lighter 
fractions   (which  have  about  the  same  compositions  with  Russian  and 
American  petroleums),  the  solubility  is  about  the  same  for  the  same  specific 
gravities,  but  for  fractions  with  specific  gravities  above  0-760,  the  difference 
in  solubility  continually  increases.     Thus,  the  corresponding  fractions  of 

1  Chem.  Zeit.,  1896,  p.  197. 

2  Journ.  de  Pharm.  et  Chim.,  1894,  XXX,  p.  289  ;  Rossi  :  Ann.  Labor.  Chim.  Gabelle, 
1900,  IV,  p.  379. 


MIDDLE  OILS   (GAS   OILS)  349 

American  and  Russian  petroleums  of  D  0-780  dissolve  respectively  in  5-2 
and  4-1  c.c.  of  the  solvent,  and  fractions  of  D  0-820  in  9-5  and  4-5  c.c.  respec- 
tively of  the  solvent. 


A  good  lamp  oil  should  be  clear  and  only  slightly  coloured  (in  time,  however, 
darkening  occurs  if  the  oil  is  exposed  to  the  air)  ;  its  odour  should  be  neither 
too  penetrating  nor  unpleasant,  as  this  would  indicate  the  presence  of  sulphur 
compounds.1  It  should  have  no  appreciable  acidity  and  should  not  turn  brown 
with  sulphuric  acid.  For  use  in  cold  places,  it  should  remain  clear  and  mobile 
at  a  temperature  lower  than  that  to  which  it  is  likely  to  be  exposed.  The 
specific  gravity  is  usually  0-780-0-805  for  American  and  0-0820-0-825  f°r  Russian 
oils. 

With  regard  to  fractional  distillation,  a  good  oil  should  not  begin  to  distil 
below  110°  and  should  contain  only  small  amounts  of  light  and  heavy  oils.  The 
limits  usually  demanded  for  ordinary  lamp  oils  are  5%  of  light  oils  and  10% 
of  heavy  oils,  but  the  proportions  actually  present  are  well  within  these  limits 
for  good  oils.  As  regards  the  fractions  comprised  between  150°  and  300°, 
there  should  be  no  great  disproportion  between  the  amounts  of  these  and  the 
middle  fractions  should  predominate  over  the  extreme. 

The  flash  point  is  of  importance  as  an  indication  of  the  danger  attending 
the  use  of  the  oil.  In  Italy,  legislation  demands  that  the  flash  point  for  lamp 
oil,  determined  by  the  Abel-Pensky  apparatus,  should  not  be  below  21°  C. 

The  viscosity  of  lamp  oil,  measured  by  the  Engler  apparatus  at  20°  C.,  is 
1-1-05,  or,  measured  by  the  Ubbelohde  apparatus,  1-10-1-80,  and  is  usually 
somewhat  lower  for  Russian  than  for  American  oils. 

The  illuminating  power  varies  with  the  lamp  used,  but,  under  ordinary  con- 
ditions, the  consumption  per  candle-hour  at  15-20°  varies  from  3-5  to  5  grams. 
The  decrease  in  luminosity  from  the  beginning  to  the  end  of  the  combustion 
is  generally  greater  with  American  than  with  Russian  petroleums.  The  latter 
burn  with  a  less  initial  and  greater  final  luminosity  than  the  former.  In  any 
case,  with  a  good  oil  the  decrease  should  not  exceed  one-fourth  of  the  initial 
value. 

Lamp  oils  from  crude  petroleums  rich  in  solid  paraffin,  e.g.,  those  from 
Boryslav,  Pennsylvania,  etc.,  if  not  properly  prepared,  deposit  solid  paraffin 
at  —  10°,  but  those  of  Russian  origin  remain  clear  even  at  —  20°. 

The  calorific  power  of  lighting  oil  is  11,000-12,000  cals. 


MIDDLE    OILS 
(Gas  Oils) 

These  are  intermediate  in  character  to  lighting  oil  and  heavy  oils.  They 
are  mobile  and  yellow  to  dark  brownish-yellow,  their  density  being  between 
about  0-845-0-855,  their  b.pt.  300-350°,  and  their  viscosity  below  3" (Engler) . 

The  most  important  determination  with  these  oils  is  the  yield  of  gas 
and  the  calorific  value  of  the  latter.  The  amount  of  gas  given  is  determined 
in  a  small  works  plant.  In  the  laboratory  it  may  be  ascertained  approxi- 
mately, in  comparison  with  a  typical  oil,  in  Ross  and  Leather's  apparatus,2 

1  According  to  Kissling  and  Engler  (Chem.  Rev.  Fett.  Ind.,  1906,  p.  158),  the  pro- 
portion of  sulphur  in  Russian  petroleums  lies  between  0-027  and  0-030%  ;   in  Galician, 
between  0-039  and  0-062%  ;    in  Pennsylvanian,  between  0-027  and  0-029%,  and  i° 
those  from  Ohio,  between  0-04  and  0-5%.     A  good  oil  should  not  contain  more  than 
0-03%. 

2  Journal  of  Gaslighting,  1906,  p.  825. 


350  HEAVY  OILS   (LUBRICATING  OILS) 

consisting  of  a  retort  (23  x  14-5  X  12  cm.)  in  which  15  c.c.  of  the  oil  are 
gasified.  The  temperature  of  gasification  is  measured  with  a  pyrometer 
and  the  volume  of  gas  produced  and  the  components  absorbable  by  fuming 
sulphuric  acid  determined. 

Another  apparatus  for  this  purpose  has  been  proposed  by  Wernecke 
and  modified  by  Hempel.1  The  results  obtained  on  the  laboratory  scale 
are,  however,  not  accurate,  the  best  method  being  the  works  test. 

The  following  determinations  may  also  be  required  :  Specific  gravity, 
behaviour  on  distillation,  flash  point,  viscosity,  calorific  power  and  sulphur, 
these  being  carried  out  as  indicated  in  the  articles  dealing  with  crude  petroleum 
and  heavy  oils. 

Middle  or  gas  oils  are  used  for  making  illuminating  gas,  for  carburetting 
water  gas,  as  a  motive  force,  as  a  cleaning  oil,  and  also  as  solvent.2 

The  yields  from  i  kilo  of  oil  vary  between  the  following  limits  :  gas,  500-600 
litres  ;  tar,  300-400  grams  ;  coke,  40-60  grams. 


HEAVY    OILS 
(Lubricating  Oils) 

These  oils  vary  somewhat  in  colour,  appearance  and  consistency.  The 
colour  is  usually  reddish,  brown  or  blackish,  and  marked  fluorescence  is 
also  observed  ;  some  such  oils  are,  however,  colourless  or  yellowish  and 
not  at  all  or  but  slightly  fluorescent  (vaseline  oil).  The  smell  is  similar 
to  that  of  lamp  oil  if  more  volatile  oils  are  present,  but  very  heavy  oils  are 
odourless.  A  bituminous  smell  indicates  faulty  refining  and  a  tarry  or 
resinous  odour  the  presence  of  extraneous  matter.  As  a  rule,  these  oils 
are  liquid  and  more  or  less  viscous,  but  some  are  highly  mobile  and  others 
have  almost  the  consistency  of  fats. 

Analysis  of  lubricating  oils  aims  at  ascertaining  if  their  characters  are 
in  correspondence  with  the  uses  for  which  they  are  designed  or  with  the 
conditions  fixed  in  the  purchase  contract. 

Both  physical  and  chemical  tests  are  made. 

1.   Physical  Tests 

1.  Colour. — This  is  usually  compared  with  that  of  a  selected  oil  by 
means  of  the  colorimeter  (see  Lighting  Oil)  or  more  simply  by  observing 
equally  thick  layers  of  the  two  oils  in  similar  rectangular  bottles. 

It  should  be  borne  in  mind  that  heavy  oils  may  be  coloured  artificially. 
Aniline  dyes  are  usually  employed  for  this  purpose  and  may  be  extracted 
from  the  oil  by  water  or  dilute  alcohol  in  presence  of  acid  or  alkali  and 
characterised  by  the  tests  to  be  given  under  the  heading,  Colouring  Matters. 

The  standard  colour  for  the  fiscal  classification  of  heavy  mineral  oils  is  that 
of  a  0-75%  solution  of  pure,  crystallised  potassium  chromate,  this  being  com- 
pared by  transmitted  light  with  the  oil  in  question  in  an  equally  thick  layer. 

1  Journal  fur  Gasbeleuchtung,  1910,  p.  78. 

2  For  this  purpose  oils  of  lower  density  and  solar  oils  from  the  distillation  of  shales 
are  also  used. 


HEAVY  OILS   (LUBRICATING  OILS)  351 

2.  Specific  Gravity. — Determined  as  with  crude  petroleum. 

3.  Distillation.— -The  flasks  used  for  crude  petroleum  are  employed. 
The  temperature  at  which  the  distillation  commences  is  noted  and  the 
distillate  up  to  300-310°,  representing  the  light  oils   and  illuminating  oil, 
collected  and  weighed. 

For  fiscal  purposes  (in  Italy) ,  the  procedure-  followed  is  that  indicated  under 
Crude  petroleum,  2.  When  decomposition  occurs,  recourse  is  had  to  distillation 
under  reduced  pressure,  as  indicated  later  for  residues. 

4.  Volatility. — When  heated,  heavy  oils  begin  to  emit  vapour  at  a 
certain  point.     To  determine  the  quantities  of  the  oil  evaporating  in  a 
certain  time  at  different  temperatures,  in  accordance  with  the  conditions 
laid  down  in  contracts,   the  following  procedure   (Holde)   is  employed  : 
The  oil-container  A  of  the  Pensky-Martens  apparatus  (Fig.  47)  is  charged  to 
the  mark  with  the  oil  and  weighed.     It  is  then  heated  for  the  prescribed 
time  ;  for  temperatures   between  100°  and  200°,  a  glycerine  bath  is  used, 
but   for  higher   temperatures  (200-300°)  a  bath   of   a  heavy  cylinder  oil 
having  a  flash  point  above  300°  is  employed. 

The  temperature  of  the  oil  is  measured  by  means  of  a  thermometer  from 
which  the  adhering  oil  is  removed  by  a  piece  of  filter-paper  (previously 
weighed  with  the  crucible),  which  is  added  to  the  oil.  After  the  experiment, 
the  oil-contained  is  cooled  in  water,  dried,  left  in  a  desiccator  for  about  30 
minutes  and  weighed  ;  the  loss  in  weight  gives  the  volatile  oil. 

With  temperatures  higher  than  300°,  the  oil  may  be  heated  directly 
in  the  Pensky-Martens  apparatus. 

5.  Flash  Point.— This  is  determined  for  heavy  oils  in  the  Pensky- 
Martens  apparatus  (Fig.  47).     The  upper  view  shows  a  section  of  the  essen- 
tial parts  of  the  apparatus.     A  is  a  brass  cylinder  similar  to  that  of  the 
Abel  apparatus  and  is  fitted  with  a  level  gauge  and  a  vaned  stirrer  a  ;   it 
is  placed  inside  an  iron  envelope  B  with  very  thick  walls.     This  part  of 
the  apparatus  is  surrounded  and  protected  from  radiation  by  a  cupola- 
shaped  brass  mantle  and  is  heated  by  means  of  a  triple  burner  C,  a  wire 
gauze  R  being  interposed.     The  cover  of  the  vessel  A  carries  a  thermometer 
t  usually  graduated  from  about  80°  to  250°,  with  its  bulb  dipping  into  the 
liquid,  and  a  gas  flame  j  which  is  brought  near  to  a  small  window  and  the 
latter  at  the  same  time  opened  by  turning  a  knob  b.     A  fixed  flame  /  serves 
to  re-light  the  movable  flame  when  this  is  extinguished  by  the  explosion. 
All  the  dimensions  of  the  apparatus  are  fixed  exactly. 

The  oil  (previously  dehydrated  with  calcium  chloride  if  it  contains 
water)  is  placed  in  the  vessel  A  and  the  apparatus  heated  to  80°,  after 
which  the  stirrer  is  started  and  the  flame  regulated  so  that  the  temperature 
rises  about  5°  per  minute.  Observations  are  made  firstly  at  intervals  of 
2°,  but  when  the  elongation  of  the  flame  indicates  the  proximity  of  the 
flash  point,  at  each  degree.  The  results  of  several  experiments  made  with 
the  same  oil  do  not  as  a  rule  differ  by  more  than  2°  or  3°  among  themselves. 

A  simpler  but  less  exact  method  of  finding  the  flash  point  of  a  heavy 
oil  consists  in  heating  the  latter  in  a  porcelain  crucible  4  cm.  in  height  and 
width,  which  is  filled  to  within  i  cm.  from  the  top  and  furnished  with  a 


352 


HEAVY  OILS   (LUBRICATING  OILS) 


thermometer.  The  crucible  is  heated  on  a  sand-bath  so  that  the  tempera- 
ture rises  about  5°  per  minute,  a  small  flame  being  brought  near  to  the  top 
of  the  crucible  at  regular  intervals  until  a  slight  explosion  occurs. 

The  results  obtained  by  these  two  different  methods  vary  in  oils  of  normal 
composition  by  5-40°  ;  the  method  employed  for  the  determination  should 
always  be  indicated. 


FIG.  47 

6.  Temperature  of  Ignition. — This  determination  may  be  made  as 
the  complement  of  that  of  the  flash  point — when  an  open  crucible  is  employed 
— by  continuing  to  heat  so  that  the  temperature  rises  from  2°  to  6°  per 
minute  ;   a  flame  is  held  for  i  -2  seconds  near  the  surface  of  the  liquid,  the 
temperature  of  ignition  being  taken  as  that  at  which  the  surface  of  the  oil 
ignites. 

The  temperature  of  ignition  is  usually  20-60°  above  the  flash  point. 

7.  Viscosity. — This  is  determined  by  means  of  viscometers,  that  of 
Engler  (Fig.  48)  being  the  one  most  used.     It  consists  of  a  covered  cylindrical 
brass  vessel  A,  the  slightly  sloping  base  of  which  is  provided  with  a  small 
central  aperture  a  leading  to  an  efflux  tube  which  can  be  shut  by  means 
of  a  wooden  plug  b.     In  the  vessel  A  are  three  points  marking  the  level  of 
the  liquid.     The  vessel  A  is  surrounded  by  a  larger  one,  the  annular  space 


HEAVY  OILS   (LUBRICATING  OILS) 


353 


FIG.  48 


between  serving  as  a  bath  to  maintain  the  temperature  constant.  Ther- 
mometers c  and  d  give  the  temperatures  in  the  vessel  A  and  in  the  bath, 
and  the  latter  is  heated  by  means  of  a  ring  burner  ;  the  whole  is  supported 
on  a  tripod.  Under  the  efflux  tube  is  a  glass  flask  C  with  marks  on  the 
neck  at  200  c.c.  and  240  c.c.  All 
the  parts  of  the  apparatus  are  of 
exactly  standardised  form  and  dimen- 
sions. 

To  make  a  determination,  the 
internal  vessel  is  filled  to  the  desired 
level  with  the  oil  to  be  examined 
(dehydrated  by  decantation  and 
filtered  through  cotton  wool  dried 
at  100°),  the  efflux  orifice  being 
shut.  The  outer  vessel  is  then  filled 
with  water  and  heated  carefully 
until  the  oil  reaches  the  temperature 
at  which  the  viscosity  is  to  be 
measured.  The  flask  is  then  placed 
underneath  and  the  plug  rapidly  _ 
withdrawn,  the  time  being  counted 
exactly  from  this  instant.  The 

exact  time  taken  to  fill  the  flask  to  the  200  c.c.  mark,  divided  by  that 
taken  under  similar  conditions,  with  a  standard  liquid,  gives  the  viscosity 
of  the  oil  in  Engler  degrees. 

Usually  a  temperature  of  20°  is  employed  and  water  taken  as  the  standard, 
and  the  apparatus  should  be  controlled  from  time  to  time  with  water  ;  as 
a  rule  52-53  seconds  are  required  for  the  efflux  of  200  c.c.  of  water. 

Between  one  determination  and  another  of  the  time  of  efflux  of  water,  the 
difference  is  _+  1-5  second,  which  corresponds  with  a  difference  of  +3%  in 
the  degrees  Engler.  If,  then,  the  difference  in* the  time  of  efflux  of  water  is 
less  than  i  sec.,  as  prescribed  for  the  use  of  the  apparatus,  the  difference  in  the 
degrees  Engler  is  +2-3%. 

Each  apparatus  is  sold  duly  controlled,  the  time  of  efflux  for  water  being 
indicated. 

For  very  dense  heavy  oils,  and  for  such  semi-solid  products  as  vaseline, 
the  viscosity  should  be  determined  at  a  higher  temperature,  e.g.,  50°,  60°, 
100°  or,  sometimes,  180°  or  even  higher.  In  the  latter  cases  the  whole 
of  the  apparatus  is  placed  in  a  large  oven,  or  use  made  of  an  apparatus  in 
which  the  outer  vessel — tightly  closed  and  fitted  with  a  reflux  condenser 
— serves  as  a  vapour- bath  in  which  water  (100°),  aniline  (180°)  or  other 
suitable  liquid  is  boiled.  In  some  cases  it  may  be  advantageous  to  determine 
the  viscosity  at  temperatures  below  20°. 

Prior  to  a  determination,  the  apparatus  should  always  be  thoroughly 
cleaned  from  every  trace  of  oil  by  washing  with  benzine  or  ether  and  drying 
with  absorbent  paper. 

The  viscosity  of  heavy  oils  constitutes  an  indirect  indication  of  their 
A.C.  23 


354  HEAVY   OILS   (LUBRICATING  OILS) 

lubricating  value  ;  the  latter  may  be  determined  directly  by  means  of  suitable 
machines,  that  of  Martens  x  being  most  commonly  employed. 

Viscometers  of  other  types  are  those  of  Lamansky-Nobel  2  (Russia),  Red- 
wood 3  (Great  Britain)  and  Saybolt  4  (America).  In  France  use  is  made  of 
Barbey's  ixometre,  which  determines  the  coefficient  of  fluidity  of  an  oil  by  measur- 
ing the  volume  of  an  oil  dropping  during  a  certain  time. 

The  ratio  between  the  values  of  the  viscosity  found  by  the  Lamansky-Nobel 
and  Engler  apparatus  respectively  is  about  constant  and  is  i -13-1-1 8  for  fluid 
oils  and  1-20-1-26  for  more  viscous  oils  (engine  and  cylinder  oils),  so  that  number 
of  Engler  degrees  =  number  of  Lamansky-Nobel  degrees  divided  by  such  factor. 

The  relations  between  Engler  values  and  those  obtained  with  the  Red- 
wood and  Saybolt  apparatus  are  given  by  the  following  formulae,  in  which  tr 
and  tt  represent  the  times  of  efflux  in  the  two  apparatus  and  E  the  Engler  degrees  : 


(2M,  =  228-7^! 

(3)  k  =  o-oSoigE  —  0-07013 


E 

In  practice,  for  viscosities  which  are  not  too  low  (not  less  than  3  or  4  degrees 
Engler),  it  is  a  sufficiently  close  approximation  to  assume  that  the  times  of 
efflux  in  the  Engler,  Redwood  and  Saybolt  forms  of  apparatus  (used  according 
to  the  conditions  prescribed  for  each  case)  are  in  the  ratios  100  :  59  :  70. 

8.  Behaviour  at  Low  Temperature. — When  strongly  cooled,  lubri- 
cating oil  first  thickens  and  ultimately  congeals  and  the  aim  of  investigating 
its  behaviour  is  either  to  ascertain  if  the  oil  remains  liquid  at  a  certain 
temperature  or  to  discover  when  it  begins  to  thicken  without  assuming 
a  tallowy  consistency. 

In  the  former  case  a  test-tube  15  mm.  in  diameter  is  filled  to  a  height 
of  about  3  cm.  with  the  oil  and  placed,  together  with  a  thermometer  in  a 
beaker  about  12  cm.  in  height  and  diameter  containing  a  salt  solution  of 
known  freezing  point 5  corresponding  approximately  with  the  temperature 
at  which  the  oil  should  remain  liquid.  The  whole  is  placed  in  an  earthen- 
ware vessel  and  cooled  for  an  hour  with  a  freezing  mixture  composed  of 
two  parts  of  snow  or  pounded  ice  and  one  part  of  common  salt.6  The  tube 
is  then  taken  from  the  solution  to  see  if  the  oil  has  remained  liquid. 

1  D.  Holde  :    Untersuchung  der  Kohlenwasserstoffole  und  Fette,  Berlin,  1913,  p.  158  ; 
W.  Hmrichsen  :    Das  Materialprufungswesen,  Stuttgart,  1912. 

2  Wischinsin  and  Singer  :    Chem.  Rev.  Fette  Industrie,  1897. 

3  B.  Redwood  :    Petroleum,  London,  1913. 

4  B.  Redwood  :    Petroleum,  London,  1913. 

5  For  this  purpose  the  following  solutions  may  be  used  : 

Freezing  point.  Composition. 


KNO3,  13  parts. 

KNO3,  13  ;   NaCl,  2. 

KNO3,  13  ;   NaCl,  3-3- 

BaCl2,  35-8. 

CaCl2,  22-5. 

NH4C1,  20. 
—  15°  to  —  15-4°   .          .          .         i   -'..-..         „        ioo      NH4C1,  25. 

6  With  this  mixture,  a  temperature  of  —  21°  may  be  attained.  For  lower  tem- 
peratures, the  two  vessels  are  charged  with  alcohol  which  is  cooled  with  solid  carbon 
dioxide  ;  constant  temperatures  of  —  25°  and  —  30°  are  thus  obtained. 


—  3°  ......     Water,  ioo 

—  4°  ......,,         ioo 

-  5°  ,,ioo 

—  8-7°  ......,,         ioo 

—  10°  ......,,  IOO 

—  14°  ......,,         ioo 


HEAVY   OILS   (LUBRICATING  OILS)  355 

In  the  second  case  a  preliminary  test  is  first  made.  The  oil  is  placed 
in  a  test-tube  through  the  stopper  of  which  passes  a  thermometer,  and 
cooled  in  a  freezing  mixture  ;  from  time  to  time  the  tube  is  withdrawn  for 
an  instant  and  inclined,  so  that  the  temperature  at  which  the  oil  begins  to 
solidify  may  be  discovered.  A  saline  solution  with  a  freezing  point  a  little 
lower  than  this  temperature  is  then  chosen  and  the  oil  kept  in  the  apparatus 
referred  to  above  at  the  temperature  found  in  the  preliminary  trial.  At 
the  end  of  the  time  the  test-tube  is  removed  from  the  solution  and  inclined 
so  that  an  idea  may  be  obtained  of  the  degree  of  thickening  ;  the  latter 
may  also  be  estimated  by  noting  the  adhesion  of  the  oil  to  a  glass  rod  when 
this  is  withdrawn. 

Supercooling  of  the  salt  solution  is  avoided  by  scraping  the  congealed 
parts  from  the  walls  of  the  containing  vessel  or  by  withdrawing  the  vessel 
itself  for  an  instant  from  the  freezing  mixture. 

If  the  cooled  oil  is  heated  and  another  examination  made  of  the  behaviour 
at  low  temperatures,  the  result  may  be  different  from  that  of  the  first  test ; 
such  difference  may  be  due  to  the  variations  of  temperature  to  which  the  oil 
is  subjected  during  transport  and  storage.  It  is  therefore  useful  to  carry  out 
the  test  on  the  oil,  first  as  received  and  then  after  it  has  been  heated  to  50° 
for  ten  minutes  and  subsequently  cooled  for  30  minutes  in  a  water-bath  at  20°. 
With  mixtures  of  mineral  and  fatty  oils,  the  cooling  should  be  protracted  for 
4-10  hours,  one  test  being  made  without  stirring  the  oil  and  the  other  with 
stirring  every  15  minutes. 

9.  Test  of  Fluidity  at  Low  Temperatures. — This  is  effected  when 
required  by  pipetting  the  oil  into  a  U-tube  of  definite  diameter  (usually 
6  mm.),  cooling  the  latter  in  a  cooling  mixture,  and  then  measuring  the 
change  of  level  produced  by  applying  at  one  side,  for  a  definite  period 
(generally  i  minute),  a  known  pressure,  e.g.,  50  mm.  of  water,  by  means  of 
a  water  manometer.  The  number  of  mm.  measuring  the  change  of  level 
represents  the  degree  of  fluidity  of  the  oil  at  the  temperature  of  the  experi- 
ment. 

2.  Chemical  Tests 

1.  Detection  of  Water  and  Solid  Substances. — These  are  usually 
recognised  by  the  appearance  and  are  investigated  as  with  crude  petroleum. 
Water  may  also  be  detected  by  heating  the  oil  in  a  test-tube  for  about  15 
minutes  :   if  water  is  present  froth  is  formed  and  drops  of  water  appear  in 
the  cold  part  of  the  tube. 

2.  Determination  of  the  Acidity. — Acidity  is  due  either  to  mineral 
acids  (sulphuric  acid)  introduced  during  refining  or  to  organic  acids. 

(a)  Acidity  due  to  mineral  acids  may  be  detected  by  shaking  50-100 
grams  of  the  oil  with  double  the  quantity  of  distilled  water,  allowing  the 
aqueous  layer  to  separate,  filtering  it  through  a  moist    filter-paper  and 
testing  about  30  c.c.  of  the  filtrate  with  a  few  drops  of  methyl  orange  solu- 
tion (0-03%)  :    when  mineral  acid  is  present  a  red  coloration  is  obtained. 

(b)  The  acidity  due  to  organic  acid  is  determined  differently  according 
as  the  oil  is  pale  or  dark.1 

1  When  the  test  for  inorganic  acidity  made  as  in  (a)  gives  a  positive  result,  the 
oil  should  be  first  subjected  to  washing  with  hot  water. 


356  HEAVY   OILS   (LUBRICATING  OILS) 

With  a  pale  oil,  10  grams  are  dissolved  in  about  150  c.c.  of  a  perfectly 
neutral  mixture  of  ether  (4  parts)  and  alcohol  (i  part)  and  the  solution 
titrated  with  decinormal  alcoholic  sodium  hydroxide  in  presence  of  phenolph- 
thalein.  If  the  colour  of  the  oil  is  too  intense  to  admit  of  observation  of 
the  colour  change  of  phenolphthalein,  10  grams  of  it  are  shaken  with  100 
c.c.  of  absolute  alcohol  and  50  c.c.  of  the  separated  alcoholic  layer  titrated 
with  decinormal  alcoholic  caustic  soda  in  presence  of  phenolphthalein.1 

The  acidity  is  expressed  as  sulphuric  anhydride  or  oleic  acid,  or  as  the 
number  of  milligrams  of  potassium  hydroxide  necessary  to  neutralise  i 
gram  of  the  oil,  the  last  being  termed  the  acidity  number  of  the  oil  ;  i% 
SO3  —  7-05%  oleic  acid  =  acidity  number  of  14. 

3.  Alkalinity.— This  is  detected  by  adding  phenolphthalein  to  another 
aliquot  part  of  the  water  with  which  the  oil  was  shaken  in  the  determina- 
tion of  the  mineral  acids  ;   with  free  alkali  a  red  coloration  is  obtained. 

It  must  be  borne  in  mind  that,  if  the  oil  in  question  contains  alkali  soaps, 
the  alkalinity  found  may  be  due  to  partial  decomposition  (hydrolysis)  of  the 
soap  by  water. 

4.  Determination  of  the  Solid  Paraffin  and  Asphalt. — As  in  crude 
petroleum  (q.v.,  Chemical  Tests,  4  and  5). 

5.  Detection    of    Oils,    Fats     and    Waxes.— (i)    QUALITATIVE.     5 
c.c.  of  the  mineral  oil  are  heated  for  about  15  minutes  in  a  test-tube  with 
a  stick  of  caustic  soda  weighing  about  4  grams,  either  over  a  naked  flame 
or,  better,  in  a  paraffin  bath  at  200-210°.     If  fatty  substances  are  present, 
even  only  to  the  extent  of  1-2%,  the  whole  mass  becomes  solid  and  gelatinous 
on  cooling. 

(2)  QUANTITATIVE.  If  the  qualitative  test  gives  a  positive  result,  the 
quantitative  estimation  may  be  carried  out  as  follows  : 

(a)  By  the  saponification  number  determined  as  indicated  for  fatty 
substances  ;  about  5  grams  of  substance  are  used  and,  besides  alcoholic 
potash,  an  equal  quantity  of  benzene  is  added,  the  heating  in  a  reflux  appara- 
tus being  continued  for  about  an  hour.  The  saponification  number  thus 
obtained  is  divided  by  1-85,  the  result  being  the  percentage  of  fatty  sub- 
stances calculated  from  the  mean  value  of  their  saponification  number. 

In  presence  of  wool  fat  or  waxes — which  are  usually  detectable  by  the  odour 
and  consistency — the  results  obtained  are  inaccurate,  since  these  substances 
have  saponification  numbers  different  from  those  of  fatty  substances. 

(6)  By  direct  weighing,  according  to  the  directions  given  by  Armani 
and  Rodano  2  : 

5  grams  of  the  oil  are  saponified  in  a  flask  with  alcoholic  potash 
solution  (12  grams  of  caustic  potash  in  100  of  alcohol),  the  flask  being 
immersed  in  a  bath  of  boiling  water.  As  reflux  apparatus,  a  simple  funnel 
is  placed  in  the  mouth  of  the  flask,  so  that  a  large  part  of  the  alcohol  is 

1  According  to  H.  Loebell  (Chem.  Zeit.,  1911,  35,  p.  276),  the  acidity  is  determined 
in  10  c.c.  of  the  oil,  using  an  alcohol-benzene  mixture  (i  :  2)  as  solvent,  alkali  blue  as 
indicator  and  decinormal  alcoholic  caustic  soda  as  standard  solution. 

2  Industria  saponiera,  Milan,  1912,  p.  169  ;    Ann.  Lab.  chim.  centrale  Gabelle,  Vol. 
VII,  p.  278. 


HEAVY  OILS   (LUBRICATING  OILS)  357 

lost  by  evaporation  ;    sufficient,  however,  remains  for  the  saponification, 
which  takes  place  fairly  rapidly  (in  about  half  an  hour). 

Without  evaporating  off  all  the  alcohol,  the  contents  of  the  flask  are 
poured  into  a  separator  and  the  flask  thoroughly  rinsed  out,  at  first  with 
small  quantities  of  alcohol  and  then  with  ether.  Sufficient  water  is  added 
to  dissolve  the  soap  formed  and  sufficient  ether  to  dissolve  the  mineral 
oil.  The  alkaline  liquid  is  almost  neutralised  towards  phenolphthalein  by 
means  of  acetic  acid  and  shaken,  a  sharp  division  occurring  on  standing 
between  the  ethereal  layer  containing  the  mineral  oil  and  the  soap  solution. 
The  ethereal  liquid  is  separated,  washed  with  distilled  water  until  the 
alkaline  reaction  disappears,  and  distilled  from  a  tared  flask,  the  last  traces 
of  ether  being  expelled  in  a  current  of  air. 

The  residue  is  dried  in  an  air-oven  at  105°  for  an  hour  and  weighed  ; 
the  weight  is  multiplied  by  20  and  the  product  subtracted  from  100,  the 
remainder  being  the  percentage  by  weight  of  the  fatty  substance. 

To  determine  the  nature  of  the  fatty  matter,  the  soap  solution  is  treated 
with  dilute  sulphuric  acid  and  the  fatty  acids  collected  and  identified  by 
their  colour  reactions  and  their  physical  characters  (see  chapter  on  Fatty 
Substances).  If  blown  or  oxidised  oils  have  been  added  to  the  mineral 
oil,  the  fatty  acids  are  brown,  have  an  odour  of  vegetable  oils  and  are  soluble 
in  ether,  from  which  they  are  partially  precipitated  by  petroleum  ether  ; 
the  precipitated  part  has  a  pitchy  appearance.  In  some  of  their  characters, 
these  fatty  acids  might  be  confused  with  those  of  fish  oils,  but  the  latter 
have  a  quite  different  odour  and  are  precipitated  by  Halphen's  bromine 
reagent  (see  Fish  Oils),  with  which  the  fatty  acids  of  oxidised  oils  give  no 
precipitate. 

When  it  is  necessary  to  examine  the  characters  of  mineral  oil  changed 
by  previous  operations,  the  saponification  is  carried  out  in  the  cold  as 
follows  : 

In  a  separating  funnel,  50  grams  of  the  oil,  200  c.c.  of  light  petroleum 
ether  and  200  c.c.  of  10%  alcoholic  potash  (in  95%  alcohol)  are  vigorously 
and  frequently  shaken  for  about  four  hours  and  then  allowed  to  settle,  the 
ethereal  layer  being  separated  and  washed  several  times  by  shaking  with 
cold  water,  and  the  petroleum  ether  evaporated  on  a  water-bath.  The 
residue  consists  of  the  mineral  oil ;  its  freedom  from  fatty  matter  may  be 
ascertained  by  determining  its  saponification  number,  which  should  be 
almost  zero. 

6.  Detection  of  Alkaline  and  Alkaline-Earthy  Soaps. — i.  QUALI- 
TATIVE. The  alkaline  soaps  may  be  dissolved  by  shaking  the  oil  with 
water,  whilst  the  alkaline-earthy  soaps  are  decomposed  by  shaking  with 
hydrochloric  acid  :  in  this  way  the  bases  pass  into  solution  in  the  hydro- 
chloric acid. 

2.  QUANTITATIVE  DETERMINATION.  About  10  grams  of  the  oil  are 
weighed,  dissolved  in  50  c.c.  of  ether,  and  shaken  in  a  separating  funnel 
with  dilute  hydrochloric  acid,  the  ethereal  solution  being  allowed  to  separate 
and  washed  repeatedly  with  water  ;  if  the  oil  is  sufficiently  clear,  alcohol 
is  added  and  the  acidity  determined,  the  fatty  acids  being  deduced  from 
the  result  obtained  (see  Fatty  Substances).  If,  however,  the  oil  is  too 


358  HEAVY  OILS   (LUBRICATING  OILS) 

highly  coloured  for  direct  titration,  the  ether  is  distilled  off,  the  residue 
treated  with  20  c.c.  of  hot  alcohol  and  the  acidity  of  the  alcoholic  liquid 
determined.  Examination  of  the  aqueous  hydrochloric  solution  will  indicate 
the  base  present  in  the  soap. 

7.  Resin    Oils. — i.  DETECTION.     Resin    oils    are    detected    by    their 
odour  and  by  Morawski's  reaction,  which  consists  in  treating  a  small  quantity 
of  the  oil  in  a  test-tube  with  acetic  anhydride  and  adding  a  drop  of  sulphuric 
acid  (D  1-53)  :  the  appearance  of  a  transient  violet  coloration  indicates  the 
presence  of  resin  oil. 

Resin  oils  may  be  detected  also  by  shaking  the  oil  (freed,  if  necessary, 
from  saponiiiable  matter)  with  an  equal  volurre  of  acetone  and  allowing 
the  two  liquids  to  separate,  the  acetone  containing  very  little  mineral  oil 
and  almost  the  whole  of  the  resin  oil.  If  the  solvent  is  evaporated,  the 
resin  oil  in  the  residue  may  be  characterised  by  the  red  coloration  which 
it  imparts  to  an  equal  volume  of  sulphuric  acid  (D  1-6),  by  its  high  specific 
gravity  (0-970-0-980)  and  by  its  rotator}'  power. 

2.  DETERMINATION.  Storch's  method  is  used  :  10  grams  of  the  oil 
(freed  from  saponifiable  matters  when  these  are  present)  are  treated  in  a 
flask,  at  a  gentle  heat  and  with  shaking,  with  50  grams  of  96%  alcohol. 
After  cooling,  the  alcoholic  liquid  is  transfeired  to  a  weighed  beaker  and 
the  oily  liquid  washed  with  a  little  alcohol,  which  is  also  added  to  the  beaker. 
The  alcohol  is  evaporated  on  the  water-bath  and  the  residue  weighed  (A). 
This  residue  is  treated  again  with  alcohol  (10  times  its  weight),  evaporation 
of  the  alcoholic  solution  giving  a  new  residue  (B).  The  mineral  oil  present 

in  this  residue  is  calculated  by  means  of  the  formula, —,  where    J 

'(«-*)' 

and  B  are  the  weights  of  the  two  residues  and  a  and  b  the  quantities  of 
alcohol  used  in  their  treatment.  Subtraction  of  the  calculated  weight  of 
mineral  oil  from  B  gives  the  quantity  of  resin  oil. 

EXAMPLE  :  10  grams  of  oil,  treated  with  50  grams  of  alcohol,  gave  a  residue 
of  1-51  gram  (A),  and  this,  treated  with  15-1  grams  of  alcohol,  gave  a  residue, 
1-15  gram  (B).  From  the  proportion 

50-15-1  :  1-51-1-15  =  15-1  :  x, 

x  =  0-155.  Amount  of  resin  oil  in  10  grams  of  the  oil  taken  =  1-15  —  0-155  — 
0-995  gram. 

8.  Tar  Oils. —  The  presence  of  tar  oils  is  recognised  besides,  by  their 
characteiistic  odour,  by  the  property  they  exhibit  of  reacting  energetically 
with  nitric  acid  (D  1-45)  giving  nitro-derivatives,  by  their  solubility  in 
cone,  sulphuric  acid  on  a  water-bath  with  formation  of  compounds  soluble 
in  water,  and  by  the  general  reactions  of  the  phenols  (see  Tar  Oils,  Car- 
bolic Acid). 

9.  Defluorescent   and    Odoriferous    Substances. —  To   destroy   the 
fluorescence  of  heavy  oils,  a-nitronaphthalene  is  usually  employed,  while 
the  unpleasant  fatty  smell  is  masked  by  addition  of  nitrobenzene.     The 
latter  is  readily  detected  by  the  odour  of  bitter  almonds  it  imparts  to  the 
oil,  whilst  the  odourless  nitronaphthalene  is  recognised  as  follows  :  Holde 
proposes  a  preliminary  test  by  heating  1-2  c.c.  of  the  oil  for  a  short  time 


HEAVY  OILS   (LUBRICATING  OILS)  359 

(0-5-1-5  minute)  with  2-3  c.c.  of  approximately  2N-alcoholic  potash :  in 
presence  of  nitro-derivatives,  a  blood-red  or  violet-red  coloration  appears. 
To  identify  the  a-nitronaphthalene,  the  following  method  (Leonard)  x  is 
used  : 

A  small  quantity  of  the  oil  is  gently  heated  with  zinc  dust  and  dilute 
hydrochloric  acid  with  occasional  shaking.  In  this  way  any  a-nitronaphtha- 
lene is  converted  into  a-naphthylamine,  recognisable  by  its  characteristic 
disgusting  odour.  The  acid  liquid  is  separated  by  means  of  a  separating 
funnel,  rendered  alkaline  with  soda  and  extracted  with  ether,  the  ethereal 
solution  being  evaporated  and  the  residue  taken  up  in  a  little  alcohol  and 
treated  with  a  drop  of  sodium  nitrite  solution  acidified  with  acetic  acid  : 
the  appearance  of  a  yellow  coloration  changing  to  crimson  indicates  the 
presence  of  a-naphthylamine. 

*  * 

Heavy  mineral  oils  have  a  specific  gravity  usually  between  0-840  and  0-930, 
although  occasionally  the  value  0-960  is  attained.  They  should  not  contain 
any  marked  quantity  of  oils  distilling  below  300°  and  their  flash  point  should 
not  be  below  the  specified  limit  laid  down  in  relation  to  the  purpose  for  which 
they  are  to  be  used.  Usually  this  temperature  is  above,  and  often  greatly 
above.  140°.  Heavy  oils  are  classified  into  numerous  types  having  the  following 
characters  : 

Light  oils  for  engines,  gearing,  motors  and  dynamos,  viscosity  mostly  13-25 
(at  20°)  and  flash  point  180-220°. 

SpindJf  oil,  very  fluid,  viscosity  3-5-15  (at  20°),  flash  point  160-200°. 

Otis  for  compressors  and  refrigerating  machines,  still  more  fluid  than  the 
preceding,  viscosity  5-7  (at  20°) ,  flash  point  140—180°  ;  the  solidification  point 
should  be  below  —  20°. 

Automobile  oils  (cylinder),  viscosity  varying  according  to  the  season  from 
20  to  85  (at  20°),  flash  point  185-215°. 

Pale  heavy  oils  for  engines  and  gearing,  viscosity  25-45  or  more  (a*  2°°) 
flash  point  190-220°. 

Dark  heavy  oils  for  locomotives  and  railway  wagons,  viscosity  25-60  (at  20°) 
and  consistency  varying  with  the  season. 

Cylinder  oils  for  steam  engines,  boiling  point  *feigh,  very  viscous  (23-60  at 
50°),  moderately  thick,  flash  point  240-315°,  or,  for  some  qualities,  350°  or 
higher.  These  oils  are  divided  further  into  low  and  high  pressure  cy Under  oils. 

Another  type  of  heavy  oil  is  that  used  for  electric  transformers.  This  should 
not  contain  water  or  mineral  acids  (reaction  neutral)  and  should  be  non- volatile  ; 
when  heated  at  100°  for  some  hours  it  should  not  decompose  (in  particular,  it 
should  not  give  solid  products  or  become  acid)  ;  it  should  retain  sufficient 
fluidity  at  —  15°  and  should  have  a  high  flash  point.  The  following  requirements 
should  be  satisfied  by  such  an  oil  :  viscosity  at  20°,  9-8  (Engler)  ;  specific  gravity, 
0-8825  '•  flash  point  (Pensky),  185°  ;  volatility,  determined  by  heating  the  oil 
for  5  hours  at  100°,  should  not  exceed  0-06%,  or  determined  by  heating  for  2 
hours  at  170°,  should  not  exceed  i%. 

All  the  oils  indicated  above  are  subdivided  into  numerous  types  indicated 
by  numbers  or  letters  or  are  sold  as  special  brands. 

Oils  to  be  used  in  the  open  air  or  in  cold  localities  should  not  become  turbid 
or  solidify  at  a  temperature  somewhat  below  the  minimum  to  which  they  may 
be  exposed.  As  a  rule  American  oils  solidify  at  o°  or  a  little  below,  whilst  those 
from  Russia  do  not  solidify  above  —  10°  or  —  20°  or  even  lower. 

1  Chem.   News,  1893,  p.  297. 


360  RESIDUES— VASELINE 

Pale  refined  oils  are  generally  free  from  acidity  or  contain  only  traces  (0-03% 
as  sulphuric  acid).  In  dark  oils,  the  acidity  may  reach  0-3%  or,  in  exceptional 
cases,  0-5%,  but  usually  it  does  not  exceed  0-15%.  Mineral  acids  should  not 
be  present. 


RESIDUES 

The  bituminous  and  pitchy  residues  from  the  distillation  of  mineral 
oils  (mazut,  astatki  or  ostatki)  are  blackish,  only  slightly  transparent,  of 
varying  consistency,  and  of  characteristic  bituminous  odour  due  to  decom- 
position products  of  difficultly  volatile  hydrocarbons. 

The  determinations  and  tests  usually  made  are  those  of  water,  specific 
gravity,  distillation,  flash  and  ignition  points,  viscosity,  solid  paraffin, 
pitch  and  asphalt,  the  methods  described  for  heavy  oils  being  employed  ; 
the  calorific  power  and  the  sulphur  are  determined  as  in  crude  petroleum. 

As  regards  distillation,  these  residues  often  decompose  at  high  tempera- 
tures with  formation  of  more  volatile  products,  so  that  distillation  by  the 
methods  already  indicated  may  yield  an  amount  of  distillate  greater  than 
the  true  value.  This  inconvenience  is  obviated  by  distilling  100  grams 
of  the  oil  at  reduced  pressure  (about  30  mm.)1  from  a  half-litre  flask  with 
a  side-tube  connected  with  a  sloping  condenser,  the  lower  end  of  which 
passes  through  a  cork  in  the  neck  of  a  distilling  flask  similar  to  that  used 
for  the  distillation  of  crude  petroleum  and  having  its  side-tube  in  com- 
munication with  an  ordinary  water  pump.  The  distillation  is  continued 
until  the  thermometer  marks  220°,  the  distillate  being  collected  in  the 
second  flask  ;  at  the  end  of  the  operation,  air  is  allowed  into  the  apparatus 
and  the  flask  containing  the  distillate  detached,  the  residue  being  then 
distilled  up  to  300-310°  at  the  ordinary  pressure. 

In  determining  the  flash  point,  the  residues  often  froth  up  at  a  tempera- 
ture near  100°  and  overflow  the  vessel.  In  such  cases  the  oil  should  be 
dehydrated  as  indicated  for  heavy  oils.  Extinction  of  the  flame  at  about 
100°  may  be  caused  by  residual  traces  of  water  in  the  product. 

When  the  residues  are  to  be  used  as  fuel,  the  essential  determinations  are 
those  of  the  calorific  power  and  sulphur  ;  the  calorific  value  is  about  10,000 
calories. 

VASELINE 

Vaselines  of  two  sorts  are  sold  :  the  natural  ones,  which  consist  of  hydro- 
carbons semi-solid  at  the  ordinary  temperature,  have  colours  varying  from 
white  to  yellowish-brown,  exhibit  slight  fluorescence  and  are  translucent, 
somewhat  sticky  and  ropy  ;  and  the  artificial  ones,  which  consist  of  solutions 
of  solid  hydrocarbons  (paraffin  wax  or  ceresine)  in  paraffin  oil  and  are 
usually  white — sometimes,  however,  yellow  or  more  or  less  brown — non- 
fluorescent,  opaque,  not  sticky  and  somewhat  granular  and  readily  separate 
paraffin  oil  at  a  low  temperature. 

The  examination  of  vaseline  aims  at  ascertaining  its  quality  and  degree 

1  Nasini  and  Villavecchia  :  Relazione  sulle  analisi  e  sulle  ricerche  esegnite  nel  Lab. 
chim.  Centrale  delle  Gabelle,  Rome,  1890,  pp.  104-106. 


VASELINE  361 

of  purity,  and  whether  it  is  natural  or  artificial.     The  tests  made  are  as 
follows  : 

1.  Suspended  Impurities. — These  are  recognised  by  their  appearance 
and  are  separated  by  fusing  the  product  and  filtering  it  in  an  oven. 

2.  Mineral  Matter.— From  0-5  to  i  gram  is  burnt  in  a  platinum  dish 
to  ascertain  if  any  weighable  residue  remains.    Any  emission  of  odours  of  resin 
or  of  burnt  fats  during  the  combustion  should  be  noted. 

3.  Solubility  in  Alcohol.     Reaction. —  One  volume  of  the  vaseline  is 
shaken  with  two  volumes  of  alcohol,  the  latter  being  separated  and  tested 
as  to  acidity  or  alkalinity  and  diluted  with  water  to  see  if  it  becomes  turbid. 

4.  Behaviour    towards    Sulphuric  Acid. — 10  grams  of   the  melted 
vaseline  are  heated  with  2-5  c.c.  of  a  mixture  of  5  parts  of  water  with  15 
parts  of  cone,  sulphuric  acid  on  a  water-bath  for  15  minutes,  with  frequent 
shaking,  any  browning  of  the  acid  or  vaseline  being  noted. 

5.  Detection    of   Fats. — 2  grams  of   the  vaseline    are   boiled  with  a 
few  c.c.  of  caustic  soda  solution,  the  cold  aqueous  layer  being  subsequently 
filtered  off  and  acidified  with  hydrochloric   acid  :    turbidity  or  separation 
of  solid  substance  indicates  the  presence  of  fats. 

6.  Detection  of  Resins. — By  Morawski's  reaction    (see  Heavy  Oils, 
Chemical  Tests,  7). 

7.  Viscosity. — By   means   of   Engler's    viscometer    (see   Heavy    Oils, 
Physical  Tests,  7),  working  at  60°  C.  and  keeping  also  the  vessel  into  which 
the  liquid  flows  hot. 

8.  Determination  of  the   Paraffin   Wax. — In  a  thin- walled,   glass 
cylinder,  20  cm.  tall  and  3-5  cm.  wide,  a  weighed  quantity  of  about  0-5 
gram  of  the  vaseline  is  dissolved  in  the  hot  in  3  c.c.  of  ether,  and  the  solution 
treated  with  50  c.c.  of  98%  alcohol.     After  being  cooled  to  o°  for  an  hour 
and  filtered  through  a  filter  also  kept  at  o°,  washing  with  a  total  quantity 
of  150  c.c.  of  98%  alcohol  maintained    at    o°  (see    Figure,  p.  338),  the 
insoluble  residue  is  dissolved  on  the  filter  in  hot  benzene  and  the  solution 
evaporated  in  a  tared  glass  dish  and  the  residue  weighed.     If  the  precipitate 
formed  in  the  tube  by  addition  of  alcohol  to  the  ethereal  vaseline  solution 
is  not  readily  detached  from  the  glass  (as  happens  especially  with  natural 
vaselines  and  with  those  containing  ceresine),  the  adherent  part  should  be 
dissolved  in  benzene  and  this  solution  added  to  that  previously  obtained. 

*  * 

Pure  vaseline  should  melt  to  a  clear  liquid  and  should  not  contain  mineral 
matter,  or  dissolve  appreciably  in  cold  alcohol,  or  exhibit  an  acid  or  alkaline 
reaction,  or  turn  sulphuric  acid  brown.  According  to  the  Italian  Pharma- 
copoeia, pure  vaseline  for  pharmaceutical  use  should  be  perfectly  neutral  and 
quite  free  from  fats,  and  should  leave  no  ash. 

Natural  vaselines  have  viscosities  varying  from  4-5  to  7-5  at  60°  C.  (referred 
to  that  of  water  at  20°  C.  and  determined  with  the  Engler  apparatus),  whilst 
the  viscosity  of  artificial  vaselines  is  usually  little  above  i  and  that  of  mixtures 
of  natural  and  artificial  vaselines  rarely  reaches  3-5.  Natural  vaselines  contain 
63-80%  of  solid  paraffin  insoluble  in  alcohol,  whilst  the  artificial  ones  contain 
only  11-35%,  and  mixtures  of  the  two  intermediate  proportions.  Ethereal 
solutions  of  natural  vaselines  are  precipitated  by  alcohol  in  the  form  of  a  sticky, 
cheesy  mass,  the  liquid  remaining  turbid  ;  with  artificial  vaselines,  a  flocculent 
precipitate  is  formed,  while  the  liquid  remains  clear. 


362 


PARAFFIN  WAX 


PARAFFIN    WAX 

Crude  paraffin  wax  is  coloured  more  or  less  intense  yellow  or  brown, 
whilst  the  refined  product  is  a  white  or  faintly  yellow,  translucent  solid. 
The  following  tests  are  made  : 

1.  Suspended  Impurities.      Reaction.     Behaviour  towards   Sul- 
phuric Acid. — As  with  vaseline  (q.v.,  i,  3  and  4). 

2.  Melting   and   Solidifying   Points. — The  melting  point   is  deter- 
mined as  with  fats,  use  being  made  of  a  capillary  tube  blown  in  the  middle 
to  a  bulb  and  with  the  lower  end  bent  upwards  after  the  substance  has 
been  introduced  (see  Fatty  Substances,  4). 

The  solidifying  point  is  determined  with  the  Shukoff  apparatus  (Fig. 
49), l  consisting  of  a  wide-mouthed  bottle  in  which  is  fixed,  by  means  of 

a  stopper,  a  tube  of  the  dimensions  and  form 
shown.  Through  the  stopper  of  this  tube  there 
passes  a  thermometer  reading  to  0-1°. 

In  the  inner  tube  30-40  grams  of  the  pro- 
duct are  melted,  and  when  the  temperature  of 
the  fused  mass  is  about  5°  above  the  solidify- 
ing point,  the  apparatus  is  shaken  vigorously 
and  regularly  until  the  contents  have  become 
distinctly  turbid  and  opaque.  The  shaking 
is  then  discontinued  and  the  thermometer 
observed. 

The  solidifying  point  is  taken  as  the  tenn- 
is   _M  perature  at    which    the    thermometer  remains 
J- — j— y  MI  \ 

L/  J?  \,L  stationary    during    the    cooling    of    the    fused 

paraffin,  or  as  the  maximum  temperature  to 
which  it  rises  after  a  short  arrest  in  the  fall. 
When  no  large  amount  of  stearic  acid  is  pre- 
sent, only  the  temperature  at  which  the  mer- 
cury remains  stationary  is  oboerved. 

3.  Determination  of  the  Paraffin  Wax 
(in  the  crude  product). — This  is  effected  by 
Holde's  method.  From  0-5  to  i  gram  of  the 
substance  is  dissolved  in  the  necessary  quantity 


FIG.  49 


of  ether,  an  equal  volume  of  absolute  alcohol  being  added  and  the  liquid 
cooled  to  — 20°,  the  subsequent  procedure  being  as  described  for  crude 
petroleum  (Chemical  Tests,  4).  The  percentage  found  is  increased  by  i, 
to  correct  for  the  amount  dissolved  in  the  solvents. 

With  soft  paraffin  waxes  this  method  gives  less  exact  although  comparative 
results. 

4.  Detection  of  Resins  and  Fatty  Acids. — Of  the  presence  of  admixed 

colophony  or  stearic  acid,  an  indication  is  obtained  from  the  acid  number, 

which  is  zero  for  pure  paraffin  wax.     If  the  product  exhibits  an  acid  number, 

5-10  grams  of  it,  finely  chopped,  are  digested,  with  frequent  shaking,  in  the 

1  Chem.  Zeit.,  1901,  p.  mi. 


CERESINE  363 

cold  with  about  200  c.c.  of  approximately  95%  alcohol ;  the  liquid  is  filtered, 
the  alcohol  evaporated  off  and  the  residue  examined.  A  yellow  or  brown 
colour  indicates  the  probable  presence  of  resin,  recognisable  by  the  reactions 
given  for  heavy  oils  (Chemical  Tests,  7)  ;  a  white  residue  probably  consists 
of  stearic  acid.  In  any  case  the  natuie  of  the  residue  may  be  ascertained 
by  determining  the  acid  and  saponification  numbers. 

5.  Detection  of  Carnauba  Wax. — This  is  often  added  in  small  pro- 
portion to  paraffin  wax  to  raise  its  melting  point.     Indications  of  its  presence 
are  given  by  the  characteristic  aromatic  odour  and  by  the  saponification 
number  (zero  for  pure  paraffin  wax).     When,  therefore,  the  product  has  a 
saponification  number,  it  is  tested  for  carnauba  wax,  the  following  method 
being  employed  :    10  grams  of  the  wax,  chopped  as  finely  as  possible,  are 
digested  for  some  hours  with  about  500  c.c.  of  ether,  with  frequent  shaking. 
After  filtration,  the  insoluble  residue- — in  which  the  carnauba  wax  is  con- 
centrated—is washed  with  ether,  pressed  between  absorbent  paper  and 
left  in  the  air  to  dry.     The  saponification  number  is  then  determined  and, 
in  presence  of  carnauba  wax,  is  markedly  higher  than  that  of  the  original 
substance.     In  doubtful  cases  the  residue  may  be  again  treated  with  ether, 
so  as  to  obtain  a  residue  still  richer  in  carnauba  wax. 

The  melting  point  of  the  insoluble  residue  is  also  determined,  this  being 
considerably  higher  than  that  of  the  original  material  if  carnauba  wax  is 
present.  Finally,  the  carnauba  wax  may  be  identified  by  decomposing  the 
soap  obtained  by  means  of  an  acid  and  determining  the  melting  point  of 
the  separated  fatty  acids. 

6.  Detection  of  Coal-tar  Colours . — Any  colour  in  the  paraffin  wax 
indicates  that  a  coal-tar  colour  may  be  present.     To  confirm  this,  the  pro- 
duct is  extracted  with  alcohol  and  the  solution  tested  as  usual  (see  Coal- Tar 
Colours). 

*** 

Refined  paraffin  wax  should  be  white  or  only  faintly  yellow,  neutral  and  free 
from,  suspended  impurities,  and  should  not  render  sulphuric  acid  appreciably 
brown.  The  melting  point  varies  somewhat  :  ordinary  hard  paraffin  waxes 
usually  melt  at  50-60°,  whilst  soft  ones  melt  below  50°  and  in  some  cases  at  30°. 
On  the  other  hand,  paraffin  wax  melting  considerably  above  60°,  like  that  from 
Java,  is  occasionally  found,  but  in  general  a  product  melting  below  60°  may  be 
regarded  as  a  paraffin  wax,  and  one  melting  between  60°  and  66°  as  a  mixture 
of  paraffin  wax  and  ceresine  (see  later).  Such  limits  are  not  valid  if  carnauba 
wax  is  present,  5%  of  this  sufficing  to  raise  the  melting  point  by  several  degrees. 


CERESINE 

Ozokerite  (crude  ceresine)  is  dark  yellow  or  brown,  but  ceresine  itself 
is  white  or  only  faintly  yellow,  opaque  and  similar  in  appearance  to  white 
wax.  The  following  tests  are  made  : 

1.  Suspended   Impurities.     Reaction.     Behaviour   towards?  Sul- 
phuric Acid. — As  in  Vaseline  (q.v.,  i,  3  and  4). 

2.  Melting  and  Solidifying  Points. — See  Paraffin  Wax,  2. 

3.  Detection  and  Determination  of  the  Paraffin  Wax. — (a)  MICRO- 


364 


SCOPIC  DETECTION.  This  is  effected  by  treating  a  little  of  the  substance 
with  hot  alcohol,  allowing  to  cool,  filtering,  and  evaporating  a  few  drops 
of  the  nitrate  on  a  slide.  A  crystalline  appearance  of  the 
residue  under  the  microscope  indicates  the  presence  of  a 
considerable  proportion  of  paraffin  wax. 

(b)  DETECTION  AND  DETERMINATION  BY  MEANS  OF  SOL- 
VENTS (by  Armani  and  Rodano's  method)  l :  This  method  is 
based  on  the  different  solubilities  of  paraffin  wax  and 
ceresine  in  a  mixture  of  absolute  alcohol  and  benzene  in 
equal  proportions. 

Use  is  made  of  the  apparatus  represented  in  Fig.  50  and 
consisting  of  a  simple  test-tube  closed  by  a  stopper  chan- 
nelled to  admit  air  and  with  a  thermometer  divided  to  0-5° 
passing  through  it ;  the  tube  is  surrounded  by  a  second 
larger  one  and  by  a  glass  cylinder  on  a  foot.  The  test-tube 
containing  o-i  gram  of  the  product  is  dissolved  in  10  c.c.  of 
the  hot  solvent,  is  placed  in  position  and  allowed  to  cool 
slowly,  the  temperature  being  noted  at  which  the  precipi- 
tation of  the  dissolved  substance  takes  place  ;  this  is  shown 
by  the  appearance  of  either  a  turbidity  or,  with  pure  paraffin 
wax  or  ceresine,  a  slight  crystalline  layer.  Since  there  is  a 
difference  of  25°  between  the  temperature  of  precipitation  of 
paraffin  wax  (25°)  and  that  of  ceresine  (50°),  the  presence 
of  even  small  proportions  of  paraffin  wax  may  be  ascer- 
tained, while  the  percentage  may  be  estimated  approximately 
by  means  of  the  following  table  : 


FIG.  50 


Paraffin  Wax. 

Ceresine 

Temperature  of 

Paraffin  Wax. 

Ceresine. 

Temperature  of 

/o 

o/ 

/o 

Precipitation. 

o/ 
/o 

o/ 
/o 

Precipitation. 

o 

IOO 

50° 

7° 

30 

40° 

10 

90 

48 

75 

25 

38 

20 

80 

47-5 

80 

20 

36-5 

30 

70 

47 

90 

10 

30 

40 

60 

44'5 

95 

5 

27 

50 

50 

43 

IOO 

— 

25 

60 

40 

4J-5 

4.  Detection  of  Resins  and  Fatty  Acids. — See  Paraffin  Wax,  4. 

5.  Detection  of  Carnauba  Wax. — See  Paraffin  Wax,  5. 

6.  Detection  of  Coal-tar  Colours. — See  Paraffin  Wax,  6. 

7.  Detection  of  added  Mineral  Matter. — This  may  be  talc,  kaolin, 
gypsum,  etc.,  and  is  detected  by  dissolving  the  product  in  benzine  and 
examining  the  residue  by  the  ordinary  analytical  methods. 


*** 


Refined  ceresine  should  be  white  or  faintly  yellow,  neutral  and  free  from 
suspended  impurities  and  should  not  render  sulphuric  acid  appreciably  brown. 

1  Ann.  Labor,   chim.  centrale  Gabelle,  Vol.  VI,  p.   109. 


MONTAN  WAX— LUBRICANTS  365 

Its  melting  point  lies  between  61°  and  78°,  although  occasionally  higher.  In 
general  a  product  with  m.pt.  above  66°  is  regarded  as  pure  ceresine.  Such 
limits  are,  however,  not  valid  if  the  ceresine  contains  carnauba  wax. 


MONTAN   WAX 
(Bergwachs) 

Montan  wax  is  obtained  by  the  treatment  of  the  lignites  of  Saxony.  In 
its  appearance  it  resembles  ozokerite  or  mineral  wax,  but  in  composition  it 
is  completely  different. 

Crude  montan  wax  is  black  or  dark  brown,  but  the  purified  product  is 
white  or  yellowish  and  of  fibrous-crystalline  appearance. 

The  determinations  made  are  usually  as  follows  : 

1.  Melting  Point.  —  As  for  paraffin  wax  (q.v.,  2). 

2.  Acidity.  —  The  product  is  dissolved  at  a  gentle  heat  in  a  mixture 
of  ethyl  and  amyl  alcohols  (i  :  2)  and  the  solution  titrated  with  decinormal 
potassium   hydroxide   solution   in   presence   of   phenolphthalein    (Holde's 
method). 

3.  Saponification  Number.  —  About  2  grams  of  the  wax  are  boiled 
for  six  hours  in  a  reflux  apparatus  with  40  c.c.  of  benzene  and  25  c.c.  of 
seminormal  potassium  hydroxide,  the  excess  of  the  latter  being  subsequently 
titrated  with  a  seminormal  acid. 

4.  Unsaponifiable  Substances.  —  2  grams  of  the  wax  are  saponified 
as  above,  the  solution  evaporated  to  dryness  on  a  water-bath  with  30  grams 
of  granular  sand,  and  the  residue  extracted  in  a  Soxhlet  apparatus  with 
petroleum  ether. 


Crude  montan  wax  has  m.pt.  80-84°,  acid  number  18-28,  Saponification 
number  80-90  ;  the  purified  product  has  m.pt.  83-84°,  acid  number  93-100, 
and  Saponification  number  94-106. 


LUBRICANTS 

Besides  heavy  mineral  oils  and  vegetable  and  animal  oils  and  fats  (see 
corresponding  chapters),  use  is  made  as  lubricants  of  mixtures  of  mineral 
oils  with  fatty  oils  (see  Heavy  Mineral  Oils)  and  of  complex  mixtures  which 
may  contain  fats,  resins,  alkaline  and  alkaline-earthy  soaps,  mineral  oils, 
resin  and  tar  oils,  in  addition  to  water  and  mineral  matter  (lime,  talc, 
graphite,  etc.). 

Of  these  complex  lubricants  the  principal  ones  are  the  stiff  lubricants, 
which  include  cart-grease  and  usually  contain  mineral  or  resin  oils  with 
lime  soaps  and  mineral  substances,  and  the  emulsive  lubricants,  formed  of 
pale  mineral  oils  with  alkaline  or  ammonium  soaps  or  sulphoricinates. 

1.  Stiff  Lubricants 

These  are  solid  or  semi-solid  products  of  varying  appearance.  In 
addition  to  noting  the  colour,  consistency,  homogeneity  and  odour,  the. 
following  tests  are  usually  made  : 


366  LUBRICANTS 

1.  Preliminary  Tests. — These  are  made  to  obtain  an  idea  of  the  com- 
position of  the  product.     The  lubricant  is  first  tested  to  ascertain  if  it  is 
completely  soluble  in  ether  and  in  petroleum  benzine  and  if  it  leaves  any 
residue  when  burnt  on  platinum  foil,  absence  of  such  residue  excluding 
the  presence  of  mineral  matter  and  soaps.     If  it  gives  with  benzene  an 
opalescent  solution,  which  becomes  clear  on  addition  of  a  little  absolute 
alcohol,  water  is  present.     The  smell  emitted  when  the  substance  is  burnt 
on  platinum  foil  gives  an  indication  concerning  the  presence  of  mineral 
oils,  resins  and  fats.     If  ash  is  left,  a  little  of  the  lubricant  is  treated  with 
a  mixture  in  equal  proportions  of  petroleum  benzine  and  absolute  alcohol, 
the  liquid  being  filtered  after  standing  for  some  hours  :  the  insoluble  residue 
is  investigated  for  lime  and  other  extraneous  mineral  substances  by  the 
ordinary  methods. 

2.  Melting  Point.- — -This  is  determined  empirically  and  approximately 
as  follows  :   The  cylindrical  bulb  of  a  thermometer  is  covered  with  the  sub- 
stance, without  heating,  until  the  shining  surface  of  the  mercury  is  no 
longer  discernible.     The  thermometer  passes  through  the  stopper  of    a 
test-tube  about  18  mm.  in  diameter,  the  tube  being  immersed  in  a  water- 
bath  which  is  gradually  heated.     The  temperature  at  which  the  substance 
begins  to  melt  at  the  surface  and  that  at  which  a  drop  of  the  fused  substance 
falls  from  the  thermometer  into  the  tube  are  noted. 

3.  Water. — On  a  boiling  water-bath,  3-5  grams  of  the  lubricant  are 
heated  in  a  tared  glass  dish  with  10-15  c.c.  of  absolute  alcohol,  the  mass 
being  stirred  until  no  further  frothing  occurs  and  the  liquid  becomes  clear. 
When  cold,  the  weight  is  again  taken,  the  loss  representing  the  moisture. 

The  latter  may  also  be  determined  by  Marcusson's  method  (see  Crude  Petro- 
leum). 

4.  Acidity. — As  a  rule,  stiff  lubricants  contain  excess  of  alkali.     When, 
however,  they  exhibit  acidity,  the  latter  may  be  determined  as  follows 
(Marcusson)  :   10  grams  of  the  lubricant  are  heated  in  a  reflux  apparatus 
with  50-100  c.c.  of  a  neutral  mixture  of  90  parts  of  benzine  and  10  of  96% 
alcohol,  any  insoluble  residue  being  filtered  off  in  the  hot  and  washed  with 
the  same  mixture.     The  filtrate  is  mixed  with  30  c.c.  of  50%  alcohol  and 
the  acidity  measured  by  titration  in  the  hot  with  normal  caustic  soda  in 
presence  of  phenolphthalein. 

5.  Detection  and  Determination  of  Soaps.— From  10  to  12  grams 
of  the  lubricant  are  shaken  vigorously  and  for  a  long  time,  in  a  250  c.c. 
separating  funnel,  with  25  c.c.  of  dilute  hydrochloric  acid  and  50  c.c.  of 
ether  ;    on  standing,  two  perfectly  clear  and  well-separated  layers  should 
be  formed.     Both  layers  should  be  tested  with  litmus  paper  to  make  sure 
that  they  are  distinctly  acid  ;  if  not,  more  hydrochloric  acid  must  be  added 
and  the  liquid  again  shaken.     The  hydrochloric  solution  is  then  separated 
and  tested  in  the  ordinary  way  for  bases,  especially  lime  and  the  alkalies, 
which  occur  in  the  soaps  employed  in  lubricants. 

The  ethereal  layer  separated  in  the  preceding  operation  is  washed  by 
shaking  with  distilled  water  until  neutral,  and  is  then  filtered  through  a 
dry  filter  into  a  weighed  flask  of  at  least  200  c.c.  capacity,  the  separating 


LUBRICANTS  367 

funnel  and  the  filter  being  washed  with  ether  ;  the  ether  is  distilled  off  on 
a  water-bath,  the  greater  part  of  it  being  condensed.  If  any  drops  of  water 
remain  in  the  flask,  they  are  eliminated  by  heating  on  a  boiling  water-bath 
after  addition  of  a  few  c.c.  of  alcohol.  The  flask  is  again  weighed  when 
cold,  the  increase  representing  the  fatty  acids  and  resins  present  either  free 
or  combined  as  soaps,  plus  the  neutral  fats  and  non-saponifiable  oils  ;  the 
percentage  of  such  substance  may  be  denoted  by  a.  The  acid  number  is 
then  determined  on  the  whole  ethereal  extract  in  the  flask  itself  ;  multipli- 
cation of  the  acid  number  by  -  -  gives  the  percentage  (b)  of  fatty  (or  resin) 

200 

acids  found  in  the  free  state  or  as  soaps.  If  from  this  is  subtracted  the 
amount  of  free  acid — -calculated  with  the  same  coefficient — found  as  under 
4  (above),  the  remainder  represents  the  acids  of  the  soap  ;  the  amount  of 
soap  is  then  calculated  in  accordance  with  the  nature  of  the  base  it  contains. 

6.  Detection  and  Determination  of  Neutral  Animal  and  Vegetable 
Oils  and  Fats. — The  liquid  remaining  in  the  flask  after  the  determination  of 
the  acidity  is  heated  on  the  water-bath  for  about  an  hour  with  excess  of 
alcoholic  potash  and  the  excess  of  the  latter  then  titrated  ;   this  gives  the 
saponification  number  of  the  neutral  fats  present.     Multiplication  of  this 

number  by  -  -  gives  the  percentage  (c)  of  neutral  fat. 
200 

7.  Investigation  of  the  Unsaponifiable   Matter. — The  amount   of 
this  may  be  ascertained  from  the  values  already  obtained  (5  and  6),  since  it 
equals  a —  (b  +  c). 

When,  however,  it  is  necessary  to  separate  and  examine  it,  the  pro- 
cedure varies  according  as  resins  or  resin  soaps  are  present  or  absent. 

In  the  latter  case,  about  50  grams  of  the  lubricant  are  shaken  vigorously 
with  at  least  200  c.c.  of  ether  in  a  separating  funnel  until  the  oils  are  dis- 
solved. A  kind  of  emulsion  holding  the  soaps  in  suspension  is  thus  formed 
and  filtration  of  this  through  a  large  pleated  filter  gives  a  clear  ethereal 
solution  containing,  besides  mineral  oils,  resin  oils  and  tar  oils,  also  any 
fats  present.  The  ether  is  distilled  off — the  last  traces  being  evaporated 
over  a  boiling  water-bath — and  the  saponification  number  determined  on 
a  part  of  the  residue.  If  there  is  any  saponification  number,  fats  are  present ; 
in  such  case,  the  non-saponifiable  oils  are  separated  by  saponification  in 
the  cold  (see  Heavy  Oils,  Chemical  Tests,  5),  and  the  mineral,  resin  and 
tar  oils  investigated  by  the  methods  indicated  for  heavy  mineral  oils. 

When,  however,  resins  or  resin  soaps  are  present,  to  separate  the  non- 
saponifiable  oils,  the  substance  is  extracted  with  acid  ether  (see  5,  above), 
the  ether  evaporated,  the  residue  washed  with  90%  alcohol  to  dissolve 
the  resin,  the  insoluble  residue  saponified  in  the  cold  (see  Heavy  Oils, 
Chemical  Tests,  5)  and  the  mineral,  resin  and  tar  oils  investigated  as 
with  heavy  mineral  oils. 

When  the  lubricant  contains  wool  fat,  a  non-saponifiable  residue  is  obtained 
which  may  be  confused  with  mineral  oils,  but  may  be  distinguished  by  deter- 
mining the  rotatory  power  and  the  iodine  number  of  the  residue  itself.  With 
mineral  oils  the  specific  rotation  is  usually  not  more  than  [a]D  =  3  and  the  iodine 
number  usually  below  6  and  only  rarely  above  14.  With  wool  fat,  the  unsaponi- 


368  LUBRICANTS 

fiable  residue  has  the  specific  rotation  +  15°  to  +  16°  or,  very  occasionally 
+  10°,  and  the  iodine  number  is  not  below  55.  Mixtures  of  mineral  oil  with 
the  unsaponifiable  matter  of  wool  fat  give  intermediate  rotations  and  iodine 
numbers.  When,  however,  the  unsaponifiable  residue  contains  resin  oils,  the 
rotatory  power  and  iodine  number  no  longer  give  an  indication  as  to  the  presence 
of  wool  fat  since  these  substances  also  absorb  iodine  and  rotate  ;  in  such  case, 
the  very  high  specific  gravity  of  resin  oils  (0-97-0-99)  must  be  borne  in  mind. 

8.  Detection  and  Determination  of  Free  Lime  and  other  Mineral 
Substances. — About  10  grams  of  the  lubricant  are  treated  for  15  minutes 
in  a  reflux  apparatus  with  5o'c.c.  of  benzine  and  5  c.c.  of  alcohol,  the  insoluble 
residue  being  collected  on  a  filter,  washed  with  the  benzine-alcohol  mixture, 
weighed  and  examined  by  the  ordinary  methods  to  see  it  it  contains  lime, 
calcium  carbonate,  barium  sulphate,  talc,  graphite  and  other  mineral  sub- 
stances. 

* 
*  * 

Stiff  lubricants  vary  in  composition  according  to  the  uses  to  which  they  are 
to  be  put.  Those  for  stuffing-boxes  in  steam-engine  cylinders  are  composed 
of  a  solid  fat  (tallow)  or  of  a  mixture  of  tallow  with  wax  and  oil.  Those  for 
ropes  contain  solid  fats,  wax,  oil,  talc,  etc.,  and  those  for  the  chains  of  cranes, 
lifts,  etc.,  are  similar.  Lubricants  for  rolling  mills  should  melt  above  100°  ; 
some  are  composed  of  pitch  from  fats  or  mixtures  of  this  with  crude  petroleum 
pitch,  while  those  with  a  basis  of  wool  fat  consist  of  partially  saponified  wool 
fat,  with  or  without  resin  or  acid  resin  oil.  Briquettes  of  vaseline,  also  used  for 
rolling  mills,  are  formed  from  mineral  oil  and  soda  soap. 

Lubricants  for  gearing  are  composed  of  a  stiff  fat  with  graphite  or  talc  ; 
oil,  tar,  resin,  wax,  paraffin  wax  and  ceresine  may  also  be  added. 

Lubricants  for  maintaining  the  flexibility  of  belting  consist  of  fish  oils  mixed 
with  a  solid  fat  (tallow,  wool  fat,  wax).  Adhesive  lubricants  for  belting  con- 
tain, besides  these  fats,  resin,  resin  oil,  wool  fat,  etc. 

Lubricants  for  the  axles  of  vehicles  usually  contain  tar  oil  or  resin  oil  in 
place  of  mineral  oil  and  mixed  lime  and  resin  soaps  in  place  of  lime  soap  and 
fatty  acids. 

2.  Emulsive  Lubricants 

These  are  colourless,  yellowish  or  reddish,  and  often  fluorescent  liquids, 
which  are  mixed  with  water  to  form  a  kind  of  emulsion  ;  they  are  some- 
times sold  ready  emulsified  and  then  have  the  appearance  of  milky  liquids. 
Besides  observing  the  colour,  transparency  and  odour,  and  determining 
the  flash  point,  viscosity  and  behaviour  at  low  temperatures  (see  Heavy 
Oils,  Physical  Tests,  5,  7  and  8),  the  following  tests  are  made  on  these  oils 
(see  also  Turkey  Red  Oil,  Chapter  XI). 

1.  Emulsivity. — -When  shaken  with  water  in  any  proportion,  the  oil 
should  give  a  milky  emulsion,  which  should  not  separate  oily  drops  at  its 
surface  even  after  a  long  rest.     When  left  overnight  at  the  ordinary  tem- 
perature, the  emulsion  of  5  grams  of  oil  with  100  grams  of  water  should 
undergo  no  change  or  should  at  most  deposit  yellowish  caseous  flocks. 

2.  Determination  of  the  Water  and  of  the  Volatile  Solvents. — The 
emulsive  oils  may  contain  volatile  solvents   (alcohol,  benzine),  which  are 
recognised  by  the  smell  or,  better,  by  distilling  the  material  on  a  water-bath 
and  examining  the  distillate.     The  amount  of  volatile  solvents  and  water, 


LUBRICANTS  369 

or  of  water  alone  when  volatile  solvent  is  absent,  may  be  determined  as 
in  stiff  lubricants  (q.v.,  3). 

3.  Detection  and  Determination  of  the  Soaps  (Fatty  Acids  and 
Alkalies). — A  preliminary  test  is  made  to  ascertain  whether  ammonia  or 
a  fixed  alkali  is  present.     Ammonia  is  detected  by  the  odour  and  reaction 
of  the  vapour  emitted  when  a  few  grams  of  the  oil  are  heated  in  a  dish  ; 
a  fixed  residue  remaining  after  calcining  indicates  the  presence  of  fixed 
alkali. 

(a)  IN  PRESENCE  OF  AMMONIA.    The  ammonia  is  determined  by  titrating 
the  aqueous  emulsion  of  the  oil  with  N/2-hydrochloric  acid  in  presence  of 
methyl  orange.     From  the  amount  of  ammonia  found,  the  quantity  of 
fatty  acids  (regarded  as  oleic  acid)  combined  with  it  is  calculated  (i  gram 
NH3  =  16-542  grams  of  C18H34O2).     The  total  fatty  acids  are  then  deter- 
mined by  boiling  the  emulsion  of  the  oil  with  a  known  quantity,  in  excess, 
of  N/io-sodium  hydroxide  solution  and  titrating  the  excess  of  alkali  with 
N/io-acid.     The  alkali  used  gives  the  total  fatty  acids  (calculated  as  oleic 
acid)  and  this  quantity,  less  the  combined  fatty  acids,  gives  the  free  fatty 
acids. 

(b)  IN  PRESENCE  OF  FIXED  ALKALI.     The  free  acids  are  determined  by 
direct  titration  of  the  acidity  in  the  usual  way,  and  the  total  fatty  acids 
by  decomposing  the  soaps  with  hydrochloric  acid,  extracting  the  fatty  acids 
with  ether,  washing  the  ethereal  layer  with  water  until  free  from  hydrochloric 
acid,  and  titrating  the  acidity  of  this  layer.     The  combined  fatty  acids  are 
then  given  by  difference.     The  aqueous  layer  is  tested  qualitatively  for 
alkalies  (see  also  Stiff  Lubricants,  5). 

(c)  IN  PRESENCE  OF  BOTH  AMMONIA  AND  FIXED  ALKALI.     The  ammonia, 
the  fatty  acids  combined  with  it,  and  the  free  fatty  acids  are  determined 
as  in  (a),  the  total  fatty  acids  as  in  (b)  and  the  fatty  acids  combined  with 
the  fixed  alkali  by  difference. 

4.  Detection  of  Unsaponifiable  Substances. — See  Stiff  Lubricants,  7. 


A.C.  24 


CHAPTER  IX 
FATTY    SUBSTANCES 

Fatty  substances  consist  essentially  of  combinations  of  various  acids 
of  the  fatty  series  with  glycerine,  and  are  obtained  from  vegetable  organisms 
(especially  seeds  and  fruits)  and  from  various  parts  of  animals.  Those 
liquid  at  the  ordinary  temperature  are  termed  oils,  and  those  solid,  fats. 

The  methods  of  analysis  of  fatty  substances  comprise  determinations 
of  certain  physical  and  chemical  properties,  commonly  known  as  constants, 
although  they  are  constant  only  within  certain  limits,  and  also  various  other 
investigations.  The  first  part  of  the  present  chapter  (General  Methods) 
contains  descriptions  of  the  more  important  determinations  and  tests  carried 
out  similarly  on  all  fatty  matters.  The  second  part  (Special  Part)  deals 
particularly  with  the  more  important  fatty  substances,  the  oils,  vegetable 
fats,  terrestrial  animal  fats  and  fats  from  fishes  and  other  marine  organisms 
being  taken  in  order.  For  each  class,  tables  are  given  showing  the  more 
important  data  relating  to  the  characters  of  the  fatty  substances  more 
commonly  sold. 

Closely  analogous  to  fatty  substances  are  the  waxes,  which  consist  of 
compounds  of  acids  with  higher  alcohols  rather  than  with  glycerine  ,  they 
will  be  treated  after  the  fats,  their  general  methods  of  analysis  being  the 
same. 

The  more  important  industrial  products  derived  from  fatty  substances, 
such  as  stearine,  oleine,  glycerine,  soaps,  candles,  etc.,  will  be  dealt  with 
in  the  next  chapter. 

GENERAL   METHODS 
1.  Preparation  of  the  Sample  and  Preliminary  Determination 

Before  analysis,  a  fatty  substance  must  be  freed  from  any  coarse  im- 
purities or  water  it  may  contain.  For  this  purpose,  a  portion  of  the  sample 
is  left  for  some  time  in  an  oven  at  about  60°,  when  it  clarifies  if  liquid  and 
melts  completely  if  solid.  It  is  then  filtered  through  one  or  more  filter- 
papers,  care  being  taken  that  any  water  collected  under  the  fat  does  not 
fall  on  to  the  filter. 

With  some  fats,  especially  industrial  fats,  the  water,  other  extraneous 
matters  (mucilaginous  substances,  residues  of  vegetable  or  animal  tissues, 
mineral  matter),  and  total  fatty  substances  have  to  be  determined.  The 
procedure  is  as  follows  : 

370 


FATTY  SUBSTANCES   (GENERAL  METHODS)  371 

A.  DETERMINATION  OF  THE  WATER.    A  flat-bottomed  dish  containing 
about  25  grams  of  coarse  siliceous  sand,  previously  ignited,  and  a  glass  rod, 
is  dried  at  100-105°  and  weighed.     About  10  grams  of  the  sample  are  then 
weighed  exactly  in  the  dish  and  mixed  well  with  the  sand.     The  dish  is 
then  heated  in  an  oven  at  100-105°  and  weighed  at  intervals  of  an  hour 
until  two  successive  weighings  are  not  appreciably  different.     The  loss  in 
weight  gives  the  water ;   the  residue  is  utilised  for  determination  C. 

B.  EXTRANEOUS  (NON-FATTY)   IMPURITIES.     An  exact  weight    (10-20 
grams)  of  the  substance  is  dissolved  in  a  beaker  in  petroleum  ether  (b.pt. 
below  70°)  by  heating  gently  on  a  water-bath.     The  solution  is  filtered 
through  a  filter  dried  at  100-105°  and  tared,  the  insoluble  matter  being 
washed  on  the  filter  with  petroleum  ether  until  a  few  drops  of  the  filtrate 
leave  no  residue  on  evaporation.     The  filter  and  its  contents  are  then  re- 
dried  at  100-105°,  and  reweighed,  the  increase  giving  the  non-fatty  matter. 

This  may  also  be  deduced  by  subtracting  water  +  total  fat  from  100. 

C.  TOTAL  FATTY  SUBSTANCE.    The  residue  from  A  is  placed  in  a  filter- 
paper  cartridge  or  capsule  and  extracted  with  ether  or  petroleum  ether 
(b.pt.   below  70°)  in  an  extraction  apparatus.     The  ethereal  solution  is 
collected  in  a  tared  dish,  evaporated  on  the  water-bath  and  the  residue 
dried  at  100°  and  weighed. 

To  obtain  the  total  fatty  matter  in  the  case  of  partially  saponified  fats 
(refinery  residues  and  similar  products)  it  is  necessary  to  treat  with  ether, 
to  shake  with  dilute  sulphuric  acid  to  decompose  the  soaps,  to  wash  the 
ethereal  liquid  with  water,  to  filter  and  evaporate  it,  and  to  dry  the  residue 
at  100°  and  weigh  it.  In  this  case  the  process  indicated  for  turkey  red 
oil  (2)  may  also  be  followed  (see  next  chapter). 

If  the  respective  quantities  of  free  and  saponified  fats  are  required,  the 
substance  is  first  extracted  alone  with  petroleum  ether,  the  extraction 
being  then  repeated  in  presence  of  an  acid. 

2.  Objective  Characters 

These  characters  are  of  importance  in  the  analysis  of  fats,  since,  from 
the  physical  condition,  colour  and  odour,  at  least  an  approximate  idea  of 
the  nature  of  the  substance  may  be  obtained.  Thus,  the  smell  is  sufficient 
to  indicate  whether  a  product  is  olive  oil,  tallow,  palm  oil,  wool  fat,  etc. 

3.  Specific  Gravity 

This  may  be  determined  by  means  of  a  Westphal  balance  or  picnometer 
at  15°  with  a  liquid  fat  or  at  a  higher  temperature  with  a  solid  fat.  In 
the  latter  case,  determinations  at  100°  are  especially  convenient  ;  the  fat 
is  placed  in  a  wide  test-tube  immersed  in  a  paraffin  bath  heated  at  100°, 
a  densimeter  or  the  float  of  a  Westphal  balance  being  immersed  in  the  fat 
when  the  latter  reaches  a  temperature  of  98°  or  100°. 

The  Italian  official  methods  prescribe  the  determination  of  the  specific 
gravities  of  oils  with  the  picnometer  or  with  the  hydrostatic  balance  to  the  fourth 
decimal  figure  at  15°.  When  the  measurements  are  made  at  higher  or  lower 
temperatures,  0-00064  ^s  added  or  subtracted  per  degree  above  or  below  15°. 

The  specific  gravity  may  give  an  indication  of  the  nature  of  an  oil  or  fat 


372 


FATTY  SUBSTANCES   (GENERAL  METHODS) 


and  serves  especially  to  distinguish  castor  oil  from  other  oils  or  fats  from  waxes, 
and  may  also  confirm  the  purity  or  otherwise  of  a  fatty  oil. 


4.  Melting  and  Solidifying  Points 

The  most  convenient  and  simple  method  for  determining  these  constants 
is  as  follows  :  Into  a  thin- walled  glass  tube  blown  to  a  small  bulb  A  at  the 
middle  (see  Fig.  51)  sufficient  of  the  fused  fat  is  sucked  to  fill  about  one- 
half  of  the  bulb.  When  the  fat  has  set,  the  branch  b  of  the  tube  free  from 
fat  is  bent  into  a  U -shape  in  a  small  flame,  and  the  tube  then  set  aside  for 
as  long  a  time  as  possible  (24  hours  if  convenient)  and,  if  the  fat  melts  at 

a  low  temperature,  in  a  cold  place.  It 
is  then  attached  by  means  of  a  platinum 
wire  or  a  rubber  ring  to  a  thermometer 
(Fig.  52)  so  that  the  fat  occupies  the 
upper  part  of  the  bulb,  and  afterwards 
suspended  in  a  beaker  of  water,  which  is 
slowly  heated.  At  a  certain  temperature 
the  fat  begins  to  melt  (at  this  point  the 
heating  is  discontinued)  and  flow  down 
the  walls  of  the  bulb  to  collect  in  the 
lower  part  of  the  bulb.  Note  is  made  of 
the  temperature  when  the  fat  begins  to 
melt  and  again  when  it  is  all  collected 
in  the  bottom  of  the  bulb.  These  tem- 
peratures represent  the  limits  between 
which  the  fat  melts,  i.e.,  its  melting 
point. 

The  fat  is  then  allowed  to  cool  slowly 
and  note  made  of  the  temperature  when 
it  begins  to  solidify  again  and  when  it  is 
all  solid,  the  solidifying  point  being  thus 
determined. 


FIG.  51 


FIG.  52 


The  solidifying  point  may  be  determined  more  exactly  by  the  method 
given  for  the  solidifying  point  of  fatty  acids  (see  Tallow,  i,  Titer  Test). 
A  similar  method  is  used  for  measuring  the  melting  points  of  fats  liquid  at 
the  ordinary  temperature  and  of  those  which  become  solid  at  very  low 
temperatures,  but  in  such  cases  it  is  necessary  to  cool  externally  with 
water  and  ice,  with  ice  alone,  or  with  a  freezing  mixture  of  snow  and 
salt. 

These  methods  are  also  used  for  finding  the  melting  and  solidifying 
points  of  the  free  acids  obtained  from  any  fat  by  saponification  (see  5, 
below). 

The  melting  and  solidifying  points,  especially  those  of  the  fatty  acids  of 
fats,  serve  to  characterise  many  of  the  latter  and  to  give  an  indication  of  their 
purity  (see  later  :  the  various  tables  of  characters  of  fats).  The  solidifying  point 
is  also  of  importance  in  the  determination  of  the  so-called  titer  of  fats  (see  Tallow). 


FATTY  SUBSTANCES   (GENERAL  METHODS)  373 

5.  Saponification 

The  object  of  this  operation  is  the  scission  of  fats  into  their  components, 
i.e.,  into  acids  and  glycerine  (or,  with  waxes,  higher  alcohols).  It  is  effected 
as  follows  :  In  a  conical  flask  or  a  porcelain  dish,  20  grams  of  the  fat  are 
heated  on  the  water-bath,  with  frequent  stirring,  with  15  c.c.  of  50%  aqueous 
caustic  potash  solution  and  30-40  c.c.  of  95%  alcohol  until  the  liquid  becomes 
homogeneous  and  clear,  this  usually  occurring  after  about  half  an  hour. 

With  substances  either  containing  higher  alcohols  (wool  fat,  waxes)  or 
mixed  with  unsaponifiable  substances  (mineral  oils,  various  extraneous 
matters),  a  clear  liquid  is  not,  however,  obtained,  since  the  action  of  the 
potash  causes  the  separation  of  the  higher  alcohols,  hydrocarbons  and  other 
unsaponifiable  substances,  which  are  usually  insoluble  under  the  conditions 
employed.  In  such  a  case  it  is  well  in  order  to  ensure  complete  saponifica- 
tion  to  prolong  the  heating  for  an  hour  or  more,  with  frequent  shaking. 
In  some  instances,  for  example,  with  wool  fat  or  waxes,  it  is  necessary  to 
carry  out  the  reaction  under  a  certain  pressure.  For  this  purpose,  use  is 
made  of  a  round-bottomed  flask,  closed  with  a  stopper  carrying  either  a 
two-bulbed  safety  funnel  charged  with  mercury  or  a  right-angled  tube 
dipping  5-6  cm.  below  the  surface  of  mercury  in  a  beaker.  In  other  cases, 
for  special  investigations  on  non-saponifiable  substances,  saponification  in 
the  cold  is  employed  ;  this  is  effected  by  dissolving  the  substance  in  ether 
or  petroleum  ether,  adding  a  considerable  excess  of  alcoholic  caustic  potash 
solution  and  shaking  for  a  long  time. 

When  the  saponification  is  finished,  the  product  (soap)  may  be  used 
for  various  purposes,  such  as  the  examination  of  the  unsaponifiable  sub- 
stances or  higher  alcohols  (see  19  :  Unsaponifiable  Substances),  the  deter- 
mination of  the  glycerine  (see  Glycerine),  or  the  separation  of  the  fatty  acids. 

For  the  last  purpose,  the  product  of  the  saponification  is  first  freed  from 
alcohol  by  prolonged  heating  on  a  water-bath,  the  residue  being  dissolved 
in  hot  water,  the  hot  aqueous  solution  shaken  well  with  excess  of  dilute 
sulphuric  acid  and  left  at  rest  on  the  water-bath  until  the  fatty  acids  are 
collected  at  the  surface  of  the  aqueous  liquid  in  a  clear  layer.  The  water 
above  the  fatty  acids  is  then  siphoned  off  and  replaced  by  fresh  hot  water, 
with  which  the  acids  are  stirred,  this  washing  being  repeated  three  or  four 
times.  Instead  of  siphoning  off  the  water,  the  latter  and  the  fatty  acids 
may  be  decanted  on  to  a  moist  filter  and  the  acids  washed  with  hot  water 
on  the  filter  itself  until  the  filtrate  ceases  to  give  the  reaction  for  sulphuric 
acid.  The  washed  fatty  acids,  in  a  flat  dish,  are  kept  for  some  time  (about 
an  hour)  in  a  steam- oven  and  then  filtered  through  a  dry  filter.  They  are 
then  ready  for  various  determinations,  such  as  the  melting  and  solidifying 
points,  acid  number,  iodine  number,  solid  and  liquid  acids. 

6.  Behaviour  towards  Solvents 

The  ordinary  solvents  for  fatty  matters  are  ether,  benzene,  carbon 
disulphide  and  tetrachloride,  chloroform  and  petroleum  ether.  All  fats 
dissolve  in  these  liquids  (castor  oil,  however,  is  aim  ost  insoluble  in  petroleum 
ether).  In  alcohol  fatty  substances  are  more  or  less  soluble  according  to 


374  FATTY   SUBSTANCES   (GENERAL   METHODS) 

their  nature  and  the  circumstances,  and  the  same  holds  with  glacial  acetic 
acid. 

The  test  of  solubility  in  the  ordinary  solvents,  e.g.,  in  ether,  serves  to  show 
if  a  fatty  substance  is  pure  or  mixed  with  extraneous  substances  insoluble  in 
that  solvent.  The  test  of  solubility  in  alcohol  may  be  used  to  distinguish  castor 
oil  and  fatty  acids  in  general  (easily  soluble  even  in  the  cold)  from  the  majority 
of  other  oils  and  fats,  which  are  mostly  very  slightly  soluble,  especially  in  the 
cold. 

7.  Acid  Number 
(Acidity  Index) 

The  acid  number  is  denned  as  the  number  of  milligrams  of  potassium 
hydroxide  (KOH)  necessary  to  neutralise  the  free  fatty  acids  in  a  gram  of 
the  fatty  substance.  From  this  number  the  amount  of  free  acids  contained 
in  a  fat  may  hence  be  deduced.  The  determination  is  made  as  follows  : 

An  exact  weight  of  about  5  grams  of  the  fat  is  heated  in  a  flat-bottomed 
flask  on  a  water-bath  with  50-60  c.c.  of  96%  alcohol,1  and  kept  well  shaken 
until  the  alcohol  begins  to  boil.  Seven  or  eight  drops  of  phenolphthalein 
solution  (i%  in  95%  alcohol)  are  then  added  and  the  liquid  titrated  with 
decinormal  potassium  hydroxide  solution  until  a  persistent  red  colour 
appears.  If  solid  fat  separates  during  the  titration,  the  flask  is  placed  on 
the  water-bath  until  the  fat  melts.  The  volume  of  potash  solution  used 
gives  the  acid  number  (i  c.c.  N/io-KOH  =0-00561  gram  KOH). 

From  the  acid  number  thus  obtained  the  percentage  of  free  acids  in 
a  fat  may  be  calculated  ;  this  is  usually  expressed  as  oleic  acid,  the  mole- 
cular weight  of  which  is  282  (corresponding  with  56-1  of  KOH).  The  calcu- 
lation is  made  by  the  formula, 

n  X  0-0282 

X  —  -  -    X   100, 

p 

where  n  is  the  number  of  c.c.  of  N/io-KOH  used,  p  the  weight  of  the  sub- 
stance and  x  the  percentage  of  oleic  acid  in  the  substance. 

The  free  acids  in  a  fat  are  sometimes  expressed  as  sulphuric  anhydride 
(SO3),  the  formula  then  becoming 

n  X  0-004 

x  =  -  -  x  100, 

P 

x  in  this  case  being  the  percentage  of  SO8. 

EXAMPLE  :  For  5-223  grams  of  fat,  4-2  c.c.  of  N/io-KOH  were  used. 
Since  i  c.c.  of  thepotash  corresponds  witho-oo56i  gram  of  KOH,  i.e.,  with  5-61 
milligrams,  the  acid  number  will  be 

5-61  X  4-2 

-  =  4'5i- 
5-223 

1  The  alcohol  should  first  be  rendered  neutral  to  phenolphthalein  by  means  of 
decinormal  caustic  potash.  If  the  fat  is  only  slightly  soluble  in  alcohol  or,  more  especi- 
ally, if  it  gives  a  highly  coloured  solution  in  alcohol,  100-150  c.c.  of  the  latter  must 
be  taken  or  a  smaller  quantity  of  substance  :  e.g.,  2  grams  are  treated  with  50-100 
c.c.  of  the  alcohol.  In  place  of  alcohol  alone,  a  mixture  of  (i)  i  vol.  of  alcohol  and 
4  vols.  of  ether,  or  (2)  i  vol.  of  absolute  alcohol  and  2  vols.  of  amyl  alcohol  may  be 
used  as  solvent,  without  heating. 


FATTY   SUBSTANCES   (GENERAL  METHODS) 


375 


Further, 

r        !      •  •  j  4-2     X    0-0282 

Percentage  of  oleic  acid  = -  X  100  =  2-267. 

5-223 

Percentage  of  SO3  =  - *  X  100  =0-321. 

5-223 

The  acidity  of  a  fat  may  also  be  expressed  in  degrees,  which  are  dis- 
tinguished as  Kottstorfer  and  Burnstyn  degrees.  The  former  represent  the 
number  of  c.c.  of  normal  KOH  solution  necessary  to  neutralise  the  free 
acidity  of  100  grams  of  a  fat. 

Burnstyn  degrees  (formerly  used,  especially  to  express  the  acidity  of 
lubricating  oils)  represent  the  number  of  c.c.  of  normal  KOH  required  to 
neutralise  the  acidity  of  100  c.c.  of  oil,  the  test  being  carried  out  as  follows  : 
100  c.c.  of  the  oil  are  shaken  with  100  c.c.  of  90%  alcohol  ;  when  the  latter 
has  separated  and  become  clear,  25  c.c.  of  it  are  titrated  with  normal  KOH, 
tincture  of  turmeric  or  phenolphthalein  being  used  as  indicator.  The 
number  of  c.c.  used,  multiplied  by  4,  gives  the  Burnstyn  acidity  of  the  oil.1 

Intercon version  of  the  acidities  expressed  in  different  ways  may  be 
effected  by  means  of  the  following  table  : 


Acid  Number 
(mgrms.  KOH  per 
gram  of  substance). 

Oleic  Acid, 
o/ 

/o 

Sulphuric  Anhydride, 
o/ 
/o 

Kottstorfer  Degrees 
(c.c.  N-KOH  per 
100  grams  of  substance). 

I 
I  -9893 

0-5027 
I 

0-0713 
0-1418 

1-782 
3-546 

14-0250 
0-5610 

7-0500 
0-2820 

I 
0-0400 

25-000 

i 

The  acid  number  of  fatty  substances  is  very  variable.  As  a  rule,  fresh  or 
recently-prepared  fats  contain  little  or  no  free  acid.  With  keeping,  especially 
if  not  well  protected  against  the  simultaneous  action  of  air  and  light,  the  acidity 
increases,  slowly  at  first  and  more  rapidly  later.  The  acid  number  is  of  impor- 
tance in  judging  edible  oils  and  lubricants,  neither  of  which  should  contain 
more  than  certain  limiting  proportions  of  free  acid. 

8.  Saponification  Number 

By  saponification  number  is  meant  the  number  of  milligrams  of  potassium 
hydroxide  (K  OH )  necessary  to  saponify  completely  i  gram  of  a  fatty  sub- 
stance. From  this  number  the  quantity  of  total  acids,  either  free  or  com- 
bined, in  a  fat  may  be  deduced.  The  determination  is  made  as  follows. 

REAGENTS  required  are  : 

(i)  Alcoholic  caustic  potash  solution  (about  seminormal).  Prepared 
by  dissolving  about  32  grams  of  pure  caustic  potash  in  a  little  water  and 
making  up  to  i  litre  with  95%  alcohol  free  from  fusel  oil.2  The  solution 

1  The  acidity  of  an  oil  determined  in  this  way  is  always  decidedly  lower  than  that 
determined  by  the  preceding  methods. 

2  When  ordinary  alcohol  is  used,  the  solution  soon  turns  brown.     Suitable  alcohol 
is  obtained  from  good,  commercial  95%  alcohol  by  adding,  and  shaking  with,  powdered 
potassium  permanganate  until  a  persistent  red  coloration  is  formed.     The  liquid  is 
left  for  some  hours  and  distilled,  in  an  apparatus  provided  with  a  dephlegmator,  with 


376  FATTY   SUBSTANCES   (GENERAL  METHODS) 

is  kept  in  a  bottle  closed  with  a  rubber  stopper  through  which  passes  a 
25  c.c.  pipette. 

(2)  Seminormal  hydrochloric  acid. 

(3)  Alcoholic  phenolphthalein  solution  (i%  in  95%  alcohol). 
PROCEDURE.     In  a  conical  150-200  c.c.  flask,  1-2  grams  of  the  fat  are 

weighed  and  treated  with  25  c.c.  of  the  alcoholic  potash  solution,  the  pipette 
being  emptied  always  in  the  same  way.  The  flask  is  closed  with  a  stopper 
through  which  passes  a  glass  tube  about  a  metre  long  to  serve  as  a  reflux 
condenser  and  heated  on  a  boiling  water-bath,  with  occasional  shaking, 
for  half  an  hour  or  rather  more  (see  Saponification,  5). 

The  flask  is  then  removed  from  the  bath  and  the  excess  of  potash  remain- 
ing free  titrated  with  seminormal  hydrochloric  acid  in  presence  of  8-10 
drops  of  the  phenolphthalein  solution.1 

A  check  experiment  with  25  c.c.  of  the  caustic  potash  solution  alone 
(without  fat)  is  made  at  the  same  time  and  under  the  same  conditions  as 
the  actual  test.2 

From  the  difference  between  the  volumes  of  seminormal  hydrochloric 
acid  used  in  the  check  experiment  and  in  the  actual  test  with  the  fat,  the 
amount  of  potash  (milligrams)  necessary  foi  the  complete  saponification 
of  i  gram  of  the  fat  is  calculated. 

EXAMPLE  :  1-524  gram  of  a  fat,  saponified  with  25  c.c.  of  alcoholic  potash, 
required  11-9  c.c.  of  seminormal  hydrochloric  acid  to  neutralise  the  excess  of 
potash.  In  the  check  experiment,  22-5  c.c.  of  the  acid  were  required  for  25 
c.c.  of  alcoholic  potash.  Since  i  c.c.  N/2-HC1  =  0-02805  gram  of  KOH,  the 
amount  of  KOH  necessary  to  saponify  1-524 gram  of  fat  is  (22-5-11-9)  0-02805 
gram  =  0-2973  gram,  so  that  the  amount  for  i  gram  of  fat  is  0-195  gram.  The 
saponification  number  of  the  fat  is  hence  195. 

The  saponification  number  is  of  importance  for  distinguishing  between 
different  fats  and  waxes  and  especially  for  the  analysis  of  mixtures  of  fatty 
substances  with  non-saponifiable  matter  (mineral  oils,  resin  oils,  etc.). 

The  majority  of  fatty  substances  have  a  saponification  number  between  190 
and  200,  but  the  oils  of  the  Cruciferse  (colza  oil,  ravison  oil,  etc.),  castor  oil, 
grapeseed  oil,  and  a  few  other  oils,  have  values  below  190. 

Coconut  oil,  palm-kernel  oil,  certain  other  vegetable  fats,  and  butter  have 
numbers  above  200.  Waxes  have  very  low  saponification  numbers  (below  100). 

9.  Ester  Number 

The  ester  number  denotes  the  number  of  milligrams  of  caustic  potash 
necessary  to  saponify  the  neutral  fat  (neutral  esters)  in  one  gram  of  a  fatty 
substance.  With  fats  which  do  not  contain  free  acids,  the  ester  number 
is  equal  to  the  saponification  number  ;  when,  however,  free  acids  are  present, 

a  little  powdered  calcium  carbonate  at  such  a  rate  that  50  c.c.  pass  over  in  20  minutes. 
To  test  the  distilled  alcohol,  10  c.c.  are  boiled  with  i  c.c.  of  50%  caustic  potash  solution 
and  the  liquid  allowed  to  stand  for  20  minutes  to  see  if  any  colour  develops.  If  so, 
the  alcohol  is  unsuitable  for  preparing  alcoholic  potash  and  should  be  again  treated 
with  permanganate. 

1  When  the  fat  gives  a  highly  coloured  solution  with  the  alcoholic  potash,  it  is 
advisable  to  dilute  the  liquid  considerably  with  neutral  alcohol  before  titrating,  in 
order  that  the  neutral  point  may  be  determined  with  accuracy. 

2  Two  blank  experiments  and  two  actual  tests  should  always  be  made  and  the 
mean  of  the  results  taken,  provided  t  hat  these  do  not  differ  greatly. 


FATTY   SUBSTANCES   (GENERAL  METHODS) 


377 


the  ester  number  is  given  by  the  difference  between  the  acid  and  saponifi- 
cation  numbers. 

The  ester  number  has  importance  especially  for  the  analysis  of  beeswax. 


10.  Volatile  Acid  Number  (Reichert-Meissl  Number) 

By  this  is  meant  the  number  of  c.c.  of  decinormal  alkali  necessary  to 
neutralise  the  volatile  acids,  soluble  in  water,  obtained  from  5  grams  of  a  fatty 
substance  under  definite  conditions. 

Reichert's  original  method  has  been  modified  in  various  ways,  the  modi- 
fication proposed  by  Leffmann  and  Beam  and  by  Polenske  being  now 
preferred. 

In  a  flat-bottomed,  300  c.c. 
flask  of  resistant  glass  (A), 
exactly  5  grams  of  the  fatty 
substance  (filtered  oil  or  mol- 
ten fat)  are  heated  over  a 
small  flame  with  20  grams  of 
pure  glycerine  and  2  c.c.  of 
caustic  soda  solution  (100 
grams  of  pure  sodium  hydro- 
xide in  100  grams  of  water) 
until  the  liquid  froths  and 
becomes  clear  and  homoge- 
neous (5-8  minutes).  The 
liquid  soap  thus  obtained  is 
allowed  to  cool  to  80-90°  and 
is  then  shaken  with  90  c.c.  of 
distilled  water  at  the  same 
temperature,  and  heated  if 
necessary,  until  solution  is 
complete.  50  c.c.  of  dilute 
sulphuric  acid  (25  c.c.  of  the 
pure  cone,  acid  to  the  litre) 
and  0-6-0-7  gram  of  roughly 
powdered  pumice  are  then 
added  and  the  liquid  distilled 
into  a  no  c.c.  flask. 

For  this  distillation  the  condenser  and  accessory  apparatus  have  the  form 
and  dimensions  (m.m.)  shown  in  Fig.  53.  The  distilling  flask  is  supported 
on  an  asbestos  card  on  a  ring  6-5  cm.  in  diameter,  and  the  flame  should  be 
such  that  the  no  c.c.  of  distillate  are  collected  in  about  19—21  minutes. 

When  the  no  c.c.  of  distillate  are  collected,  the  flame  is  extinguished 
and  the  collecting  flask  replaced  by  another  vessel  and  left  in  water  at  15° 
without  shaking  for  10  minutes.  It  is  then  stoppered,  inverted  four  or  five 
times  to  mix  the  liquid  but  not  to  shake  it  too  much,  and  filtered  through 
a  dry  filter  8  cm.  in  diameter,  loo  c.c.  of  the  filtrate  being  titrated  with 
decinormal  potassium  hydroxide  solution  in  presence  of  3-4  drops  of  i% 


FIG.  53 


378  FATTY  SUBSTANCES   (GENERAL  METHODS) 

alcoholic  phenolphthalein  solution.  The  number  of  c.c.  of  N/io-alkali 
required,  increased  by  one-tenth,  represents  the  volatile  acid  number. 

For  each  series  of  determinations  a  blank  experiment  must  be  made 
with  the  same  glycerine  (20  grams),  sodium  hydroxide  solution  (2  c.c.) 
and  sulphuric  acid  (50  c.c.)  and  under  the  same  conditions  as  in  the  actual 
test.  The  number  of  c.c.  of  N/io-alkali  used  in  this  blank  experiment 
is  subtracted  from  the  volume  used  in  the  actual  test. 

The  determination  of  the  volatile  acid  number  may  be  carried  out  along 
with  that  of  the  Polenske  number  (see  Butter,  15,  in  Chapter  II  of  Vol.  II), 

The  Italian  official  method  for  determining  the  volatile  acid  number  is, 
for  oils,  Wollny's  modification  of  the  Reichert-Meissl  method,  and  for  butter, 
Leffmann  and  Beam's  modification,  which  differs  from  that  described  above 
in  using  a  glycerine  and  soda  solution  previously  prepared  (125  c.c.  of  glycerine 
and  25  c.c.  of  5%  sodium  hydroxide  solution  heated  until  the  water  is  eliminated) 
in  place  of  glycerine  and  soda  separately,  and  in  a  few  other  detailis. 

The  volatile  acid  number  is  of  importance  in  the  analysis  of  only  a  limited 
number  of  fats,  principally  butter.  With  most  oils  and  fats,  the  number  is 
less  than  i  ;  coconut  oil,  palm-kernel  oil,  croton  oil,  cacao  butter  and  a  few 
other  fats  have  numbers  above  i  (up  to  14),  while  for  butter  the  value  is  28. 
Some  fish  oils  and  other  marine  animal  oils  (dolphin,  whale)  have  variable  and 
sometimes  moderately  high  volatile  acid  numbers. 


11.  Acetyl  Number 

This  represents  the  number  of  milligrams  of  potassium  hydroxide  corre- 
sponding with  the  quantity  of  acetyl  (C^H30)  combining  with  i  gram  of 
fat  or  wax,  or,  more  usually,  with  i  gram  of  fatty  acids  or  higher  alcohols 
(unsaponifiable  substances)  obtained  from  a  fat  or  wax. 

This  number  is  determined  as  follows  :  About  20  grams  of  the  substance 
or  of  the  free  fatty  acids  obtained  in  the  manner  described  under  "  Saponi- 
fication  "  (see  5,  above)  or  of  unsaponifiable  substances  (high  alcohols,  etc.) 
obtained  as  indicated  under  "  Non-saponifiable  Substances  "  (see  19,  below) 
are  boiled  for  2  hours  with  an  equal  volume  of  acetic  anhydride  in  a  flask 
fitted  with  a  reflux  condenser,  the  mixture  being  subsequently  transferred 
to  a  beaker,  mixed  with  500  c.c.  of  hot  water  and  boiled  for  half  an  hour. 
The  supernatant  water  is  then  siphoned  off  and  the  residue  again  washed 
in  the  same  way,  this  treatment  being  continued  until  the  water  no  longer 
becomes  acid  ;  this  usually  requires  four  or  five  washings.  The  acetylated 
product  is  then  filtered  through  a  dry  paper  in  an  oven  at  100°  and  used 
for  the  determination  of  the  acidity  number — known  as  the  ccelyl  acid  value 
— and  the  saponification  number- — the  acetyl  saponification  number.  The 
acetyl  number  is  given  by  the  difference  between  these  two. 

For  these  determinations,  3-5  grams  of  the  acetylated  product  are 
dissolved  in  50  c.c.  of  90%  alcohol  and  the  solution  titrated  with  seminormal 
potassium  hydroxide  solution  in  presence  of  phenolphthalein  ;  this  gives 
the  acetyl  acid  number.  The  same  liquid  is  then  boiled  for  a  short  time 
in  a  water-bath  with  excess  of  N/2-KOH  and  alcohol  and  the  excess  of 
alkali  titrated  with  N/2-HC1,  this  giving  the  acetyl  saponification  number. 

EXAMPLE  :    3-402  grams  of  acetylated  fatty  acids  from  castor  oil  required 


FATTY  SUBSTANCES    (GENERAL  METHODS)  379 

for  neutralisation  17-3  c.c.  of  N/2-KOH,  i.e.,  17-3  X  0-02805  —  °'4&5'2  gram 
KOH,  the  acetyl  acid  value  being  therefore 

485-2 

^  J     =  142-6. 

3-402 

After  addition  of  a  further  quantity  of  30  c.c.  of  N/2-KOH  and  boiling,  11-5 
c.c.  of  N/2-HC1  were  necessary  to  neutralise  the  excess  of  potash.  The  potash 
consumed  in  the  saponification  of  the  acetyl  compounds  was  hence  30-11-5  = 
18-5  c.c.,  corresponding  with  18-5  X  0-02805  =  O'S1^  gram  KOH  ;  for  i  gram 
of  acetylated  acids  the  amount  of  KOH  will  be 

518-9 

-  =  152-5- 
3-402 

The  acetyl  number  is  therefore  152-5,  and  the  acetyl  saponification  number, 
142-6  +  152-5  =  295-1. 

The  acetyl  number  is  related  to  the  quantities  of  hydroxylated  acids  and 
higher  alcohols  in  the  fatty  substances,  these  being  especially  large  in  castor 
oil,  grapeseed  oil,  waxes  and  blown  or  oxidised  oils.  It  is  consequently  of 
some  importance  for  the  identification  of  these  fats  and  for  the  analysis  of 
waxes. 

12.  Iodine  Number 

This  expresses  the  number  of  grams  of  iodine  100  grams  of  a  fatty  sub- 
stance are  capable  of  fixing  under  definite  conditions.  It  may  be  determined 
in  the  two  following  ways  : 

A.  Hiibl's  Method. —  REAGENTS  required: — 

1.  Iodine    solution.       25    grams    of    iodine    are    dissolved    in     500 
c.c.  of  95%  alcohol  (puriss.)  ;   in  another  500  c.c.  of  the  same   alcohol,  30 
grams  of  mercuric  chloride  are  dissolved  and  the  solution  filtered,  if  neces- 
sary.    The  two  solutions  are  stored  separately  in  tightly  stoppered  bottles 
in  a  cold  dark  place,  equal  volumes  of  them  being  mixed  in  the  quantities 
required  for  the  number  of  tests  to  be  made,  about  48  hours  before  use. 

2.  Potassium   iodide  solution.     10  grams   of  potassium  iodide  (puriss.) 
quite  free  from  iodate  are  dissolved  in  100  c.c.  of  water. 

3.  Starch    solution.     I  gram  of    starch    is  made    into  a  paste    with  a 
little  cold  water  and  then  poured  into  about  300  c.c.  of  boiling  water,  stirred 
and  left  to  settle  ]  when  cold,  the  clear  supernatant  liquid  is  poured  off  for 
use  as  indicator.     Soluble  starch  also  may  be  employed,  this  being  prepared 
by  digesting  potato  starch  with  dilute  hydrochloric  acid  (D  1-05)  for  a 
week,  then  washing  with  water  by  decantation  until  the  washing  water 
is  free  from  hydrochloric  acid  and  drying  between  filter-papers  at  a  moderate 
temperature  ;    i  gram  of  this  starch  is  dissolved  in  100  c.c.  of  hot  water. 

4.  Sodium    thiosulphate    solution.     25    grams    of    crystallised    sodium 
thiosulphate     (puriss.)     are     dissolved    in     distilled    water     to     i     litre, 
and  the  strength  of  the  solution  determined  by  Volhard's  method,  as  follows  : 
20  c.c.  of  a  solution  containing  3-863  grams  of  pure  potassium  dichro- 
mate  per  litre  are  shaken  with  10  c.c.  of  the  aqueous  10%  potassium  iodide 
solution  and  5  c.c.  of  hydrochloric  acid  (D  i-io)  ;    100-150  c.c.  of  water 
are  then  added  and  the  liberated  iodine  titrated  with  the  sodium  thio- 
sulphate solution,  a  little  of  the  starch  paste  being  added  towards  the  end 
of  the  titration.     Since  20  c.c.  of  the  above  potassium  dichromate  solution 
set  free  0-2  gram  of  iodine  from  potassium  iodide  in  presence  of  hydrochloric 


380  FATTY   SUBSTANCES    (GENERAL   METHODS) 

acid,  the  number  of  c.c.  of  thiosulphate  used  corresponds  with  0-2  gram 
of  iodine. 

5.  Chloroform,  which  should  be  pure. 

PROCEDURE.  In  a  thin  glass  bulb  the  fatty  substance  (as  it  is,  if  liquid, 
or  fused  if  a  solid,  but  always  previously  dehydrated  and  filtered  :  see  i  : 
Preparation  of  the  Sample)  is  weighed,  0-1-0-2  gram  being  taken  of  a  drying 
oil,  0-2-0-3  gram  of  a  semi-drying  oil,  0-3-0-4  gram  of  a  non-drying  oil  or 
0-4-0-8  gram  of  a  solid  fat.  The  bulb  is  placed  in  a  half-litre  glass  bottle 
with  a  tight  ground  stopper,  the  bottle  being  held  obliquely  and  suddenly 
shaken  so  as  to  break  the  bulb  against  the  walls.  The  fat  is  then  dissolved 
in  15  c.c.  of  chloroform  and  treated  with  25  c.c.  of  the  mixture  in  equal 
volumes  of  the  iodine  and  mercuric  chloride  solutions  (prepared  about  48 
hours  earlier),  care  being  taken  in  all  cases  to  empty  the  pipette  in  the  same 
way  so  that  exactly  the  same  volume  of  solution  is  used.  The  liquid  is 
carefully  shaken  and  the  bottle  stoppered  and  kept  in  a  dark  cool  place 
(15-18°)  for  4-6  hours  with  non-drying  or  semi-drying  oils  or  for  18-24 
hours  with  drying  oils.  At  the  end  of  this  time,  15-20  c.c.  of  the  potassium 
iodide  solution  are  introduced,  the  stopper,  neck  and  walls  of  the  bottle 
being  washed  with  this  solution  and  with  about  200  c.c.  of  distilled  water 
subsequently  added.  The  excess  of  iodine  is  then  titrated  with  the  thio- 
sulphate solution,  which  is  slowly  run  in  until  the  aqueous  liquid  and  the 
chloroform  beneath  appear  only  pale  yellow  ]  about  5  c.c.  of  the  starch 
solution  are  then  added  and  the  titration  completed. 

This  test  is  always  made  in  duplicate  and  at  the  same  time  two  blank 
experiments  are  carried  out  with  the  same  proportions  of  solutions  and 
under  the  same  conditions,  but  without  the  fatty  substance.  The  amounts 
of  iodine  in  the  two  checks  are  titrated  one  before  and  the  other  after 
the  actual  test,  the  mean  value  being  taken. 

This  mean  is  deducted  from  the  mean  value  obtained  in  the  testf-  with 
the  fat,  the  remainder  representing  the  amount  of  iodine  absorbed  by  the 
fat,  and  this,  calculated  as  percentage,  is  the  iodine  number. 

B.  Wijs's  Method. — In  this  method,  the  alcoholic  solution  of  iodine 
and  mercuric  chloride  is  replaced  by  an  acetic  acid  solution  of  iodine  mono- 
chloride  prepared  as  follows  : 

8  grams  of  pure  iodine  trichloride  and  8-5  grams  of  iodine  are  dis- 
solved separately  in  pure  glacial  acetic  acid  (99%)  on  a  water-bath  and  in 
dry,  closed  vessels  to  avoid  absorption  of  moisture.  When  cool,  the  two 
solutions  are  transferred  to  the  same  i-litre  flask  and  made  up  to  volume 
with  pure  glacial  acetic  acid. 

It  is  necessary  to  ascertain  that  the  acetic  acid  is  at  least  99%  and  that 
it  is  pure  :  when  heated  with  potassium  dichromate  and  cone,  sulphuric 
acid  ic  should  give  no  coloration  even  after  some  time. 

Further,  to  dissolve  the  fatty  substance  use  is  made  of  pure  carbon 
tetrachloride  (also  to  be  tested  with  dichromate  and  sulphuric  acid,  as  with 
the  acetic  acid). 

The  solutions  4,  2  and  3  (sodium  thiosulphate,  potassium  iodide  and 
starch)  of  Hubl's  method  are  used  also  in  this  case. 

The  procedure  is  the  same  as  with  Hubl's  method,  excepting  that  the 


FATTY  SUBSTANCES   (GENERAL  METHODS)  381 

time  of  contact  of  the  fatty  substance  with  the  iodine  solution  is  reduced 
to  about  an  hour  for  non-drying  or  but  slightly  drying  oils  and  fats  and  to 
about  two  hours  for  the  others.  The  calculation  is  made  as  with  Hubl's 
method. 

EXAMPLE  :  For  0-352  gram  of  olive  oil  24-90  c.c.  of  thiosulphate  were 
required,  and  in  the  check  experiment,  48-80  c.c.  The  quantity  necessary  to 
decolorise  the  excess  of  iodine  is,  therefore,  48-8  —  24-9  =  23-90  c.c. 

Assuming  that  0-2  gram  of  iodine  corresponds  with  16-5  c.c.  of  thiosulphate, 
i.e.,  0-01212  gram  with  i  c.c.,  the  amount  of  iodine  absorbed  by  0-352  gram 
of  the  oil  is  23-9  x  0-01212  =0-2896  gram,  so  that  the  iodine  number  is 

0-2896  x  ioo 

0-325 

As  a  rule  the  iodine  numbers  obtained  by  the  second  method  (Wijs's)  are 
rather  higher  than  those  given  by  Hubl's  method. 

The  determination  of  the  iodine  number  is  of  great  importance  for  the  analysis 
of  fatty  substances,  since  it  serves  to  characterise  many  of  them  and  to  indicate 
if  they  are  pure  or  mixed.  Drying  oils  (linseed,  hempseed,  walnut,  poppy- 
seed,  madia,  Japan  wood,  etc.)  and  fish  oils  (sardine,  anchovy,  herring,  cod) 
have  very  high  iodine  numbers,  which  usually  exceed  120.  The  non-drying 
oils  (olive,  arachis,  almond)  have  iodine  numbers  below  ioo.  The  semi-drying 
oils  (colza,  cottonseed,  sesame,  maize)  have  intermediate  values.  Iodine  num- 
bers between  30  and  60  are  usually  shown  by  vegetable  fats,  excepting  coconut 
oil,  palm-kernel  oil  and  certain  so-called  vegetable  waxes  (myrtle,  Japan), 
which  have  values  below  n.  With  the  animal  fats  the  iodine  number  is  not 
very  high,  being  usually  less  than  90. 

With  each  individual  fat  the  iodine  number  may  vary  between  fairly  wide 
limits,  in  accordance  with  the  method  of  preparing  the  fat,  with  the  degree 
of  maturity  of  the  fruit  or  seed  yielding  it,  with  the  conditions  of  storing  and 
age  of  the  fat,  etc.  Very  wide  variations  are,  however,  exceptional,  and  in 
most  cases  the  iodine  number  keeps  moderately  constant  (see,  for  example, 
Olive  Oil),  so  that  it  may  be  used  for  the  approximate  determination  of  the 
respective  quantities  of  fats  in  a  mixture  of  two  of  known  character — the  calcu- 
lation being  made  according  to  the  law  of  mixtures. 

The  causes  of  pronounced  variations  in  the  iodine  number  are  various,  but 
of  especial  importance  are  the  age  and  storage  conditions  of  the  fat.  In  general, 
old  and  badly  stored  (rancid)  fats  have  iodine  numbers  lower  than  those  of 
the  corresponding  fresh  and  well-kept  fats  ;  this  is  notably  the  case  with  drying 
oils,  which  readily  absorb  atmospheric  oxygen. 


13.  Absolute  or  "  Inner  "  Iodine  Number 

This  represents  the  weight  of  iodine  absorbable  by  ioo  parts  of  the 
liquid  fatty  acids  obtainable  from  a  fatty  substance.1  It  is  determined 
on  the  liquid  fatty  acids  isolated  by  Tortelli  and  Ruggeri's  process  (see  later  : 
18). 

Ten  or  fifteen  drops  of  the  liquid  acids,  just  prepared,  are  weighed  in 
a  bulb  of  thin  glass  and  the  iodine  number  then  determined  as  indicated 
in  the  preceding  article  (12). 

1  It  is  the  liquid  portion  of  the  fatty  acids,  separated  as  described  later,  that  con- 
tains the  unsaturated  fatty  acids  (oleic,  linoleic,  linolenic,  etc.),  which  have  the  property 
of  fixing  iodine,  so  that  the  iodine  number  of  this  portion  is  properly  called  the  absolute 
iodine  number. 


382  FATTY  SUBSTANCES   (GENERAL  METHODS) 

The  absolute  iodine  number  follows  the  same  course  as  the  relative  one, 
being  very  high  in  the  drying  oils  (over  150)  and  the  semi-drying  oils  (120-155) 
and  lower  in  the  non-drying  oils  (about  ico).  For  animal  fats  the  number  is 
usually  90-100,  but  in  rare  cases  slightly  exceeds  ico  (in  some  American  lards). 
This  number  is  of  especial  importance  in  the  analysis  of  lard  and  its  substitutes 
(see  Lard). 

14.  Insoluble,  Fixed  Fatty  Acid  Number 
(Hehner  Number) 

This  number  represents  the  quantity  of  non- volatile  fatty  acids  insoluble 
in  water  contained  in  100  grams  of  a  fatty  substance.  Its  determination 
is  carried  out  as  follows  : 

5  grams  of  the  fat,  weighed  into  a  conical  flask,  are  treated  with  50 
c.c.  of  90%  alcohol  and  5  c.c.  of  50%  caustic  potash  solution.  The  flask 
is  closed  with  a  stopper  through  which  passes  a  long  glass  tube  to  serve  as 
reflux  condenser  and  is  then  heated  on  a  water-bath  with  frequent  shaking 
until  saponification  is  complete.  The  stopper  and  tube  are  then  removed 
and  the  alcohol  distilled  off,  the  last  traces  being  expelled  from  the  open 
flask  in  a  boiling  water-bath.  The  soap  is  dissolved  in  150  c.c.  of  hot  water 
and  then  decomposed  with  a  slight  excess  of  dilute  sulphuric  acid.  The 
flask  is  then  left  on  the  water-bath  until  the  fatty  acids  have  collected  in 
a  homogeneous  layer  at  the  surface,  after  which  it  is  allowed  to  cool  some- 
what and  kept  in  cold  water  (at  10-15°)  for  about  an  hour,  so  that  the  fatty 
acids  set  to  a  solid  mass.  The  aqueous  liquid  is  then  filtered  through  a 
smooth,  thick  paper  filter,  previously  dried  at  100°  and  weighed  in  a  weighing 
bottle.  A  further  quantity  of  200  c.c.  of  hot  water  is  added  to  the  flask, 
which  is  shaken,  left  on  the  water-bath  for  15  minutes,  allowed  to  cool 
somewhat  and  placed  in  cold  water,  the  aqueous  liquid  being  filtered  as 
before.  This  treatment  is  repeated  five  or  six  times  until  the  filtrate  no 
longer  reddens  a  litmus  paper  immersed  in  it  for  10  minutes.  The  fatty 
acids  are  then  completely  melted  by  addition  of  a  little  boiling  water  and 
the  whole  transferred  to  the  filter,  the  flask  being  freed  from  the  last  traces 
of  the  fatty  acids  by  several  small  quantities  of  hot  water,  and  care  taken 
that  a  few  drops  of  water  always  remain  under  the  acids  on  the  filter.  When 
all  the  acids  are  on  the  filter,  all  the  water  on  the  latter  is  allowed  to  flow 
away  and  the  filter  immediately  placed  carefully  in  the  weighing  bottle, 
which  is  dried  at  100°  and  weighed  at  the  end  of  each  half-hour  until  the 
difference  between  two  successive  weighings  is  less  than  i  milligram.  The 
weight  of  the  fatty  acids  thus  obtained,  calculated  for  100  grams  of  sub- 
stance, gives  the  insoluble  fixed  acid  number  sought.1 

The  insoluble  fatty  acid  number  varies  little  for  most  oils  and  fats,  being 
usually  95-96-5  for  oils  and  94-5-97  for  fats.  Some  vegetable  and  animal  oils 
and  fats  are,  however,  exceptional,  especially  if  they  are  rich  in  volatile  or 

1  With  highly  altered  fats,  which  may  contain  appreciable  proportions  of  hydroxy- 
acids,  or  with  fats  which  may  be  mixed  with  gummy  or  gelatinous  substances,  etc. 
(such  as  sanse  oils  or  bone  oils),  it  is  well  to  treat  the  insoluble  fatty  acids  with  cold 
carbon  disulphide  or  petroleum  ether  to  remove  hydroxy-acids  and  other  extraneous 
substances  (Gianoli  :  Ann.  Soc.  chim.  de  Milano,  1902,  p.  155). 


FATTY   SUBSTANCES   (GENERAL  METHODS)  383 

soluble  fatty  acids.  Thus  the  following  oils  :  Cretan  Elliotianus,  curcas,  grape- 
seed,  Macassar,  palm-kernel,  cacao,  coconut,  dogfish,  dolphin  (from  the  head), 
have  values  varying  from  87  to  94  ;  dolphin  oil  (from  the  jaw),  spermaceti 
and  wool  fat,  from  59  to  66.  The  number  for  butter  is  86-90,  and  those  for 
the  waxes  are  also  comparatively  low. 

15.  Hydroxy -acids 

The  determination  of  the  quantity  of  hydroxy-acids  contained  in  a 
fatty  substance  is  effected  by  Fahrion's  method,  based  on  the  insolubility 
of  the  hydroxy-acids  and  the  solubility  of  all  the  fatty  acids,  in  light  petro- 
leum. 

From  3  to  5  grams  of  the  fatty  substance  are  saponified  in  the  usual 
way  (see  5  :  Saponification),  the  alcohol  evaporated,  the  soap  dissolved  in 
50-70  c.c.  of  hot  water,  decomposed  in  a  separating  funnel  with  dilute 
hydrochloric  acid,  shaken  well  with  100  c.c.  of  petroleum  ether  (boiling 
below  80°)  and  left  until  the  two  separate  layers  are  perfectly  clear.  The 
aqueous  layer  is  run  off  and  then  the  petroleum  ether,  the  insoluble  hydroxy- 
acids,  which  remain  adherent  to  the  walls  of  the  funnel,  being  washed  several 
times  with  petroleum  ether  and  afterwards  dissolved  in  boiling  alcohol. 
The  alcoholic  solution  is  evaporated  to  dryness  in  a  tared  dish  and  the 
residue  dried  at  100°  and  weighed. 

This  method  allows  of  the  determination  of  the  hydroxy-acids  produced 
by  the  oxidation,  either  natural  or  artificial,  of  an  oil  or  fat.  Such  a  determina- 
tion has  special  importance  in  the  analysis  of  boiled  linseed  oil  and  of  the  so- 
called  blown  oils,  which  are  rich  in  hydroxy-acids. 

16.  Lactones  or  Internal  Anhydrides 

The  simplest  method  of  determining  the  content  in  internal  anhydrides 
of  a  mixture  of  fatty  acids  is  based  on  the  following  principle  :  in  a  mixture 
of  pure  insoluble  fatty  acids  it  is  found  that  the  acid  number  is  equal  to 
the  saponification  number,  so  that  there  is  no  ester  number.  If,  however, 
the  fatty  acids  are  accompanied  by  lactonic  anhydrides,  the  saponification 
number  differs  from  the  acid  number.  This  is  because  the  fatty  acids  are 
saturated  immediately  in  the  cold  by  potash,  whilst  the  lactones  must  be 
boiled  with  excess  of  alcoholic  potash  in  order  to  be  neutralised. 

Hence,  to  ascertain  the  content  in  lactones  of  a  mixture  of  fatty  acids, 
it  is  sufficient  to  determine  by  the  ordinary  methods  the  acid  number  and 
the  saponification  number  and,  consequently,  the  ester  number.  From 
the  latter  the  content  of  lactone  may  be  calculated,  when  the  molecular 
weight  from  which  the  ester  number  is  calculated  is  known  (usually  the 
lactone  content  is  calculated  as  stearolactone). 

In  order  that  the  acid,  saponification  and  ester  numbers  of  the  fatty 
acids  may  not  be  confused  with  the  respective  numbers  for  the  fatty  sub- 
stances, it  has  been  proposed  to  call  the  former  :  Constant  acid  number, 
constant  saponification  number  and  constant  ester  number. 

EXAMPLE  :  If  a  mixture  of  fatty  acids  gives  the  constant  acid  number 
1 60  and  the  constant  saponification  number  195,  the  constant  ester  number 
will  be  35. 


384  FATTY  SUBSTANCES   (GENERAL  METHODS) 

The  ester  number  of  stearolactone  being  198-9,  the  mixture  examined  con- 
tains 


of  stearolactone. 

The  determination  of  the  lactones  is  of  some  importance  with  certain  indus- 
trial products  of  fatty  matters,  e.g.,  turkey  red  oil  and  distilled  stearine,  the 
latter  especially  being  rich  in  stearolactone,  i.e.,  in  the  internal  anhydride  of 
hydroxystearic  acid. 

17.  Determination  of  the  Glycerine 

The  simplest  method  of  determining  if  glycerine  is  present  in  a  substance 
is  to  heat  a  little  of  the  latter  to  boiling  with  a  few  crystals  of  potassium 
bisulphate  :  in  presence  of  glycerine,  unpleasant,  irritating  odours  of  acrolein 
are  evolved,  while  a  strip  of  filter-paper  soaked  in  concentrated  sodium 
nitroprusside  solution  containing  a  little  piperidine  is  dyed  an  intense  blue 
if  placed  in  the  mouth  of  the  test-tube. 

The  glycerine  in  fatty  substances  may  be  determined  indirectly,  knowing 
that  in  the  saponification  of  neutral  fats  i  mol.  of  glycerine  (92  grams) 
corresponds  with  3  mols.  of  potassium  hydroxide  (168-3  grams).  Multipli- 
cation of  the  ester  number  (see  9,  above)  by  0-05466  also  gives  the  glycerine 
content.  This  method  is,  however,  only  applicable  when  the  fat  does  not 
contain  higher  alcohols,  unsaponifiable  substances,  etc. 

To  determine  the  glycerine  directly,  the  fatty  substance  (20  grams)  is 
saponified  in  the  ordinary  manner  (see  5  :  Saponification),  the  soap  decom- 
posed by  an  acid,  the  fatty  acids  separated  by  filtration,  and  the  glycerine 
in  the  aqueous  filtrate  determined  by  one  of  the  methods  given  in  the  next 
chapter  for  the  quantitative  analysis  of  glycerine. 

18.  Determination  of  the  Solid  and  Liquid  Fatty  Acids 

The  fixed  (or  insoluble)  fatty  acids  entering  into  the  composition  of 
fatty  substances  may  be  divided  into  two  principal  groups  :  solid,  saturated 
acids  belonging  to  the  acetic  acid  series  and  represented  especially  by  stearic 
and  palmitic  acids  (sometimes  also  by  arachic  and  lignoceric  acids),  and 
liquid,  unsaturated  fatty  acids  belonging  to  the  acrylic  series  and  to  other 
less  hydrogenated  series  and  represented  especially  by  oleic  acid  and  often 
also  by  linoleic,  linolenic  and  ricinoleic  acids. 

The  best  method  for  separating  these  two  groups  of  acids  is  based  on 
the  insolubility  of  ^  the  lead  salts  of  the  solid  acids,  and  the  ready  solubility 
of  those  of  the  liquid  acids,  in  ether.  Special  methods  serve  for  the  separa- 
tion of  the  individual  solid  acids  and  the  individual  liquid  acids. 

1.  Separation  and  Determination  of  the  Solid  and  Liquid  Acids.  — 
For  such  separation  Tortelli  and  Ruggeri's  method  is  used  : 

20  grams  of  the  fat  are  saponified  in  the  usual  way  (see  Saponifi- 
cation), the  soap  being  dissolved  in  water  and  the  solution  neutralised 
towards  phenolphthalein  with  acetic  acid.  Meanwhile,  300  c.c.  of  7% 
neutral  lead  acetate  solution  are  heated  in  a  conical  flask  and  when  this 
liquid  reaches  the  boil  the  soap  solution  is  run  into  it  in  a  thin  stream,  the 
lead  solution  being  kept  stirred.  The  flask  is  then  immersed  in  cold  water 


FATTY  SUBSTANCES    (GENERAL  METHODS)  385 

for  about  10  minutes  with  continual  shaking,  the  lead  soap  becoming  attached 
to  the  sides  and  bottom  of  the  flask,  while  the  liquid  becomes  clear.  The 
whole  of  the  liquid  is  then  decanted  off  and  the  soap  washed  with  three 
successive  quantities  of  200  c.c.  of  hot  water  (70-80°).  The  water  is  drained 
off,  the  beaker  cooled,  the  last  drops  of  water  adhering  to  the  soap  removed 
by  means  of  filter-paper,  and  220  c.c.  of  ether  added.  The  flask  is  well 
shaken  and  then  fitted  with  a  reflux  apparatus  and  the  liquid  gently  boiled 
on  a  water-bath  for  20  minutes  with  occasional  shaking  and  subsequently 
immersed  in  cold  water  (4-5°)  for  two  hours.  The  clear  ether  is  filtered 
into  a  separating  funnel,1  care  being  taken  to  let  as  little  as  possible  of  the 
undissolved  soap  fall  into  the  filter.  The  residue  in  the  flask  is  then  heated 
for  20  minutes  with  a  fresh  quantity  of  100  c.c.  of  ether  under  a  reflux  con- 
denser and  the  flask  afterwards  stoppered  and  placed  on  one  side  immersed 
in  cold  water. 

Meanwhile  the  filter  is  washed  with  a  little  very  cold  ether  which  is 
caught  in  the  separating  funnel  containing  the  other  filtrate.  The  well- 
covered  filter  is  placed  on  one  side,  while  the  ethereal  liquid  in  the  separating 
funnel  is  vigorously  shaken  with  150  c.c.  of  20%  hydrochloric  acid  to  decom- 
pose the  lead  soap  of  the  liquid  acids  and  then  left  to  stand  until  the  ether 
has  collected  at  the  surface  in  a  clear  layer.  The  lower  aqueous  layer, 
together  with  the  precipitated  lead  chloride,  is  run  off,  the  treatment  repeated 
with  100  c.c.  of  hydrochloric  acid,  and  the  ethereal  solution  then  washed 
three  times  with  distilled  water  (150  c.c.  each  time).  Finally,  the  bulk  of 
the  ether  is  distilled  off  and  the  last  traces  driven  off  on  a  water-bath  while 
a  current  of  carbon  dioxide  is  passed. 

The  liquid  acids  thus  obtained  are  weighed  and  calculated  to  100  parts 
of  the  substance.  These  liquid  acids,  provided  they  are  kept  out  of  contact 
with  the  air,  may  be  further  utilised  for  the  detection  of  cottonseed  oil 
and  sesame  oil  (q.v.)  and  for  the  determination  of  the  absolute  iodine  number 
(see  13,  above). 

The  lead  soap  of  the  solid  fatty  acids,  left  undissolved  in  the  flask  im- 
mersed in  cold  water,  is  collected  on  the  filter  placed  on  one  side,  as  men- 
tioned above,  and  washed  well  with  very  cold  ether  and  then  introduced 
into  a  separating  funnel  where  it  is  shaken  with  ether  and  hydrochloric  acid 
as  in  the  case  of  the  liquid  acids. 

The  ethereal  solution  of  the  solid  fatty  acids  is  distilled  and  the  residue 
dried  in  an  oven  at  100°  and  weighed.  For  greater  accuracy,  the  weight 
found  may  be  increased  by  the  quantity  of  solid  acids  (stearic  and  palmitic) 
corresponding  with  their  lead  soap  remaining  dissolved  in  the  ether,  knowing 
that  50  c.c.  of  anhydrous  ether  at  the  ordinary  temperature  dissolve  0-0074 
gram  of  lead  stearate  and  0-0092  gram  of  lead  palmitate  ;  these  amounts 
correspond  with  0-0054  gram  of  stearic  and  0-0065  gram  of  palmitic  acid. 
The  solid  acids  thus  separated  may  then  be  utilised  for  other  investigati  3ns, 
e.g.,  for  that  of  the  arachidic  and  lignoceric  acids  (see  Arachis  Oil). 

Other  gravimetric  methods  for  the  quantitative  separation  of  the  solid 
from  the  liquid  fatty  acids  are  (i)  those  of  David z  and  Falciola,3  based  on 

1  For  very  exact  determinations  the  funnel  should  be  cooled  externally  with    ice. 
z  Ann.  de  chim.  analyt.,  1911,  p.  8.       3  Gazz.  chim.  ital.,  1910,  II,  pp.  217  and  425, 

A.c.  25 


386  FATTY   SUBSTANCES   (GENERAL  METHODS) 

the  fact  that  the  ammonium  salts  of  the  solid  acids  are  insoluble,  and  those 
of  the  liquid  acids  soluble,  in  alcohol,  and  (2)  that  of  Fachini  and  Dorta,1 
based  on  the  insolubility  of  the  solid  fatty  acids  and  their  alkali  salts  in 
cold  acetone  ;  this  solvent  also  serves  to  separate  stearic  and  palmitic 
acids  from  myristic  and  lauric  acids. 

The  content  of  liquid  and  solid  acids  in  a  fatty  substance  may  also  be 
deduced  from  the  absolute  and  relative  iodine  numbers.  If  Ir  is  the  relative 
iodine  number  or  that  of  the  fat  as  such,  and  Ia  the  absolute  iodine  number 
or  that  of  the  liquid  fatty  acids  extracted  from  the  fat,  i  part  by  weight  of 

iodine  corresponds  with  —  parts  by  weight  of  liquid  acids  (since  Ia  corre- 

a 

sponds  with  100  parts  by  weight  of  liquid  acids).     With  the  quantity  of 

iodine  I r  absorbed  by  100  parts  of  the  fat  there  correspond  -  — r  parts  of 

•*« 
liquid  fatty  acids,  this  last  fraction  giving  the  percentage  of  liquid  fatty 

acids  in  the  fatty  substance. 

When  a  mixture  of  palmitic,  stearic  and  oleic  acids  along  is  dealt  with, 
the  content  of  oleic  acid  may  be  calculated  from  the  relative  iodine  number 
of  the  mixture,  since  it  is  known  that  the  theoretical  iodine  number  of  oleic 
acid  is  90-07.  Thus,  if  /  is  the  relative  iodine  number  of  the  mixture  and 
0  the  percentage  of  oleic  acid  sought, 

100  X  / 

O  =  -  or  0  =  i-iioz/. 

90-07 

Lastly,  it  must  be  pointed  out  that,  with  mixtures  of  the  three  acids 
named  above,  the  content  of  liquid  and  solid  acids  may  be  determined  by 
means  of  the  solidification  point  of  the  mixture,  use  being  made  of  Dalican's 
table  (see  Tallow  and  Stearine,  i). 

2.  Determination  of  the  Stearic  Acid.— The  content  of  stearic  acid 
in  a  mixture  of  fatty  acids  obtained  by  saponification  of  a  fat  may  be  deter- 
mined by  Hehner  and  Mitchell's  method,  which  is  based  on  the  fact  that 
stearic  acid  is  very  slightly  soluble  in  alcohol  at  o°,  whilst  palmitic  acid  is 
much  more  soluble  and  the  liquid  acids  readily  soluble. 

From  0-5  to  i  gram  of  the  fatty  acids,  if  solid,  or  5  grams  if  liquid,  are 
dissolved  in  100  c.c.  of  alcohol  of  D  =  0-8183  (94-4%  alcohol)  already 
saturated  at  o°  with  pure  stearic  acid  ;  the  solution  is  then  cooled  to  o° 
and  filtered  and  the  residue  washed  with  alcohol  saturated  with  stearic 
acid,  working  always  at  o°  ;  finally  the  stearic  acid  remaining  insoluble  is 
weighed. 

This  method  is  applicable  especially  to  mixtures  of  stearic  acid  with  palmitic 
and  oleic  acids,  which  are  the  most  common  ;  with  more  complex  mixtures 
it  does  not  give  satisfactory  results.2 

3.  Determination  of  the  Stearic  and  Palmitic  Acids. — With  a 
mixture  of  solid  fatty  acids  free  from  liquid  acids  and  composed,  as  is  the 

1  Rend.  Soc.  chim.  ital.,  1912,  p.  51. 

•  2  On  the  solubility  of  the  various  acids  in  alcohol,  see  also  a  paper  by  Kreis  and 
Hafner  in  Zeit.  Unt.  Nahr.  und  Genussmittel,  1903,  p.  22,  and  also  papers  by  Heiduschka 
and  Burger  and  by  Serger  in  Zeits,  fur  offent,  Chem.,  1913,  pp.  87  and  131. 


FATTY  SUBSTANCES   (GENERAL  METHODS) 


387 


more  general  case,  of  stearic  and  palmitic  acids,  the  respective  proportions 
of  these  two  acids  may  be  determined  from  either  the  acid  number  or  the 
melting  point  of  the  mixture. 

The  following  table  of  Mangold  and  Marazza  gives  the  proportions  of 
stearic  and  palmitic  acids  in  a  mixture  of  the  two  acids,  on  the  basis  of  the 
acid  number. 

TABLE    XLII 
Stearic  and  Palmitic  Acids  from  the  Acid  Number 


Acid  Number 

i 
100  parts  of  mixture 
contain                         A^  Number 

ioo  parts  of  mixture 
contain 

(mgrms.    of 

(mgrms.  of 

KOH  per  gram 
of  mixture). 

Stearic 
Acid. 

Palmitic 
Acid. 

KOH  per  gram 
of  mixture). 

Stearic 
Acid. 

Palmitic 
Acid. 

197-50 

IOO 

208-86 

45 

55 

198-50 

95 

5 

209-95 

40 

60 

199-50 

90 

10 

211-06                    35 

65 

200-50 

85 

15 

212-18                    30 

70 

201-50 

80 

20 

213-30                    25 

75 

202-50 

75 

25 

214-45                          20 

80 

203-50 

7° 

30 

215-60 

15 

85 

204-60 

65 

35 

216-77 

10 

90 

205-60 

60 

40 

217-95 

5 

95 

206-70 

55 

45 

219-13                     o 

IOO 

207-77 

50 

50 

The  following  table  gives  the  stearic  and  palmitic  acids  contained  in  a 
mixture  of  these  two  acids  in  relation  to  the  melting  point  of  the  mixture, 
according  to  Heintz  and  according  to  Hehner. 


TABLE  XLIII 
Palmitic  and  Stearic  Acids  from  the  Melting  Point 


Melting  Point. 

Solidifying 

Palmitic  Acid. 

Stearic  Acid. 

Point. 

% 

o/ 

/o 

Heintz.                    Hehner. 

62-0° 

61-8° 

IOO 

o 

60-1 

59-o 

54-5° 

90 

10 

57-5 

56-5 

53-8                        80 

20 

55-i 

54-2 

54-0                        70 

3^> 

56-3 

55'5 

54-5 

60 

40 

56-6 

55-6 

55-o 

50 

50 

60-3 

59-4 

56-5 

40 

60 

62-9 

61-5 

59'3 

30 

70 

65-3 

64-2 

60-3 

20 

80 

67-2 

66-5 

62-5 

10 

90 

69-2 

68-5 

- 

IOO 

388  FATTY   SUBSTANCES   (GENERAL  METHODS) 

19.  Unsaponifiable  Substances 

By  unsaponifiable  substances  in  fatty  matters  is  usually  meant  both 
substances  which  are  not  attacked  by  the  alkali  during  the  saponification, 
such  as  mineral  oils,  resin  oils,  solid  paraffin  and  ceresine — which  are  un- 
saponifiable in  the  strict  meaning  of  the  term — and  also  substances  which 
are  liberated  by  the  saponification  itself  and  separate  owing  to  their  slight 
solubility  under  the  conditions  of  saponification,  such  being,  for  instance, 
the  higher  alcohols  (ceryl  and  myricyl  alcohols,  cholesterol  and  phytosterol). 

The  latter  substances  form  an  integral  part,  i.e.,  enter  into  the  con- 
stitution, of  many  fatty  matters  and  waxes,  while  the  former  (mineral  oils 
and  the  like)  may*  be  added  artificially  to  fats. 

To  separate  the  unsaponifiable  substances  from  fats  it  suffices  to  saponify 
in  the  usual  way  (see  5),  to  dissolve  the  soap  in  water  and  shake  the  solution 
with  ether  or  petroleum  ether  (b.pt.  below  80°),  to  separate  the  two  liquids 
and  evaporate  the  ethereal  solution,  which  will  leave  the  unsaponifiable 
matters.  To  prevent  emulsification,  which  often  occurs  when  an  alkali 
soap  is  shaken  with  ether,  a  little  alcohol  may  be  added  and  a  larger  quantity 
of  ether  used. 

To  determine  quantitatively  the  unsaponifiable  substances,  it  is  more 
convenient  and  accurate  to  work  as  follows : 

20  grams  of  the  substance  to  be  examined  are  saponified  by 
boiling  with  15  c.c.  of  50%  caustic  soda  solution  and  50  c.c.  of  95%  alcohol 
for  about  30  minutes,  the  liquid  being  then  transferred  to  a  dish  and  the 
alcohol  evaporated,  8-10  grams  of  sodium  bicarbonate  (to  transform  the 
excess  of  caustic  alkali  into  carbonate)  and  70-80  grams  of  siliceous  sand 
being  gradually  mixed  in.  When  the  whole  is  quite  dry  it  is  placed  in  a 
thick  filter-paper  thimble  and  extracted  in  an  extraction  apparatus  with 
petroleum  ether  (b.pt.  below  80°).  The  solvent  is  subsequently  extracted, 
the  residue,  dried  at  100°  and  weighed,  giving  the  quantity  of  unsaponifiable 
matter. 

The  unsaponifiable  matters  which  may  be  extracted  from  fats  in  this 
way  or  by  the  other  methods  given  under  particular  cases  (see  Tallow,  3, 
Detection  of  Phytosterol)  are  mainly  as  follows  : 

1.  Higher  Alcohols. — These  are  divided  into  those  of  the  aliphatic 
series  (cetyl,  ceryl,  myricyl)  and  those  of  the  aromatic  series  (cholesterol, 
phytosterol).  The  former,  which  occur  especially  in  waxes,  are  solid  and 
melt  at  moderately  high  temperatures — cetyl  alcohol  at  50°,  ceryl  at  79° 
and  myricyl  at  85° ",  they  are  soluble  in  alcohol,  from  which  they  crystallise 
readily,  and  they  dissolve  in  and  combine  with  boiling  acetic  anhydride, 
the  solution  remaining  liquid  on  cooling  provided  that  a  sufficient  excess 
of  acetic  anhydride  were  used. 

The  aromatic  higher  alcohols  are  found  in  almost  all  fats,  although  often 
in  very  small  proportions. 

Cholesterol  occurs  in  fats  of  animal  origin.  It  is  soluble  in  hot  alcohol, 
from  which  it  crystallises,  on  cooling,  in  nacreous  leaflets  having  the  appear- 
ance of  rhombic  plates  under  the  microscope  (Fig.  54).  It  melts  at  145-150° 
and  dissolves  in  boiling  acetic  anhydride,  the  cold  solution  depositing  a 


solid  acetyl  compound  which,  when  purified  and  recrystallised  from  alcohol, 
melts  at  114-115°.  If  a  solution  of  a  little  cholesterol  in  2  c.c.  of  chloroform 
is  shaken  with  an  equal  volume  of  concentrated  sulphuric  acid,  the  chloro- 
form solution  assumes  a  red  coloration, 
which  soon  changes  to  cherry-red  and 
then  to  violet-red,  this  persisting  for  some 
days,  whilst  the  acid  liquid  turns  reddish 
brown  ;  if  a  few  drops  of  the  chloroform 
solution  are  shaken  in  a  porcelain  dish,  the 
colour  changes  successively  to  blue,  green 
and  dirty  yellow. 

Phytosterol  or  sitosterol  (cholesterol  from 
plants]  occurs  in  fatty  substances  of  vege- 
table origin.  It  dissolves  in  alcohol,  from 
which  it  crystallises  in  tufts  of  broad, 
blunt-ended  needles,  having  the  micro- 
scopic appearance  of  elongated,  blunted  plates  (Fig.  55),  m.pt.  135-144°. 
When  boiled  with  acetic  anhydride,  phytosterol  also  gives  an  acetyl-com- 
pound,  m.pt.  125-137°  (purified  and  recrystallised).  With  chloroform  and 
sulphuric  acid  it  behaves  like  cholesterol. 


FIG.  54 


FIG.  55 


FIG.  56 


When  a  mixture  of  cholesterol  and  phytosterol — which  may  be  obtained 
from  a  mixture  of  animal  and  vegetable  fats  or  oils — is  crystallised  from 
alcohol,  the  crystals  show  the  predominant  form  of  the  phytosterol  (Fig. 
56)  and  melt  at  temperatures  intermediate  to  the  melting  points  of  choles- 
terol and  phytosterol  (see  also  Lard). 

2.  Paraffin  Wax.     Ceresine. — These  are  solid  and  are  insoluble  in 
alcohol,  aniline  and  acetic  anhydride,1  and  hence  distinguishable  from  the 
higher  alcohols. 

3.  Mineral  Oils,  Tar  Oils,  Resin  Oils. — These  are  liquids  and  are 
readily  recognisable  by  their  appearance  and  odour.     Resin  oils  are  also 
characterised  by  their  reaction  with  sulphuric  acid  (see  Resin  Oils)  or  by  their 
rotatory  power  (+  30°  to  +  50°  in  a  200  mm.  tube),  and  the  mineral  oils 


1  If  acetic  anhydride  is  boiled  for  a  long  time  with  paraffin  wax  or  ceresine,  the 
latter  dissolves,  but  the  solution  becomes  turbid  as  soon  as  the  flame  is  removed. 


390  FATTY   SUBSTANCES   (GENERAL  METHODS) 

by  their  insolubility  in  alcohol  or  aniline,  in  which  solvents  tar  oils  and 
resin  oils  dissolve., 

20.  Detection  and  Determination  of  the  Resin 

Resin  (colophony)  l  is  often  found  mixed  with  fatty  substances  (especi- 
ally boiled  linseed  oil  for  varnishes  and  the  like),  waxes,  and  particularly 
soaps. 

1.  Qualitative  Investigation. — With  neutral  fats  or  oils,  fatty  acids, 
or  waxes,  5-10  grams  of  the  substance  are  heated  to  boiling  for  a  few  moments 
with  as  much  70%  alcohol  and  the  alcoholic  liquid  allowed  to  cool,  filtered 
off  and  evaporated  :    the  colophony,  which  is  easily  soluble  in  alcohol, 
remains  as  residue  and  is  identifiable  by  its  general  characters  and  by  means 
of  the  following  reaction  (Morawski's)  : 

A  small  quantity  of  colophony,  dissolved  in  1-2  c.c.  of  acetic  anhydride 
and  then  treated  with  1-2  drops  of  sulphuric  acid  of  D  1-53  (34-7  c.c.  of 
sulphuric  acid  of  66°  Baume  plus  35-7  c.c.  of  water),  gives  a  transient,  violet- 
red  coloration. 

A  similar  reaction  is,  however,  given  by  cholesterol  when,  for  instance, 
wool  fat  may  be  present.  In  such  case  the  residue  from  the  evaporation 
of  the  alcoholic  liquid  is  taken  up  in  dilute  potassium  hydroxide  solution 
(which  readily  dissolves  colophony),  the  liquid  being  shaken  with  ether 
(which  dissolves  cholesterol)  and  the  aqueous  alkaline  liquid  acidified  and 
the  resin  acids  thus  obtained  tested  by  means  of  Morawski's  reaction. 

With  soap,  about  5  grams  are  dissolved  in  water  and  the  solution  shaken 
with  ether,  the  aqueous  liquid  being  acidified  and  the  fatty  acids  tested  by 
Morawski's  reaction. 

2.  Quantitative  Investigation. — When  mixed  with  fatty  substances 
or  with  soaps,  colophony  may  be  determined  by  Twitchell's  method,  which 
is  based  on  the  fact  that,  in  alcoholic  solution,  the  acids  of  the  resin  are 
not  esterified  by  gaseous  hydrogen  chloride,  whilst  fatty  acids  are  readily 
converted  into  ethyl  esters  under  these  conditions.     The  procedure  is  as 
follows  : 

The  mixture  of  fats  and  resin  is  saponified  in  the  usual  way  and  the 
fatty  acids  then  separated  by  acidifying  the  soap  solution.  In  the  case 
of  a  soap,  this  is  dissolved  in  water  and  the  solution  filtered  and  then  decom- 
posed by  acid.  With  mixtures  containing  unsaponifiable  substances  it  is 
necessary,  after  saponification,  to  extract  the  liquid  with  benzene  or  petro- 
leum ether  to  remove  the  unsaponifiable  matter,  the  aqueous  solution  being 
then  decomposed  with  an  acid.  The  fatty  and  resin  acids  thus  obtained 
are  well  washed  and  dried  and  2-3  grams  dissolved  in  50  c.c.  of  absolute 
alcohol  and  dry  hydrogen  chloride  gas  passed  into  the  solution  kept  at 
about  10°  by  immersion  in  water  and  ice.  The  current  of  gas  is  stopped 
after  i|  hour,  when  the  saponification  is  complete.  After  an  hour's  rest, 
the  liquid  is  diluted  with  5  vols.  of  water  and  boiled  until  the  esters,  mixed 
with  resin  acids,  float  in  a  clear  layer  and  the  alcohol  is  then  eliminated. 

The  resin  acids  may  then  be  determined  either  volu metrically  or  gravi 
metrically. 

1  For  its  characters,  see  Colophony,  Vol.  II,  Chapter  IX. 


FATTY   SUBSTANCES   (GENERAL  METHODS) 


391 


(a)  Volumetrically.  The  product  of  the  esterification  is  dissolved  in 
ether  and  washed  repeatedly  with  water  to  eliminate  the  mineral  acid  and 
then  diluted  with  50  c.c.  of  neutral  alcohol  and  titrated  with  N/io-potassium 
hydroxide  in  presence  of  phenolphthalein  :  i  c.c.  N/io-KOH  =  0-0346 
gram  of  resin. 

(b)  Gravimetrically .  The  esterification  product  is  dissolved  in  50  c.c.  of 
petroleum  ether  (b.pt.  below  80°),  shaken  well,  and  the  aqueous  acid  liquid 
separated.  The  petroleum  ether  solution  is  washed  with  water  and  shaken 
with  50  c.c.  of  an  aqueous  solution  containing  0-5  gram  of  caustic  potash 
and  5  c.c.  of  alcohol.  The  resin  acids  pass  into  the  aqueous  alkaline  solu- 
tion, whilst  the  fatty  esters  remain  dissolved  in  the  petroleum  ether.  The 
alkaline  aqueous  liquid  is,  therefore,  separated  and  acidified,  the  resin  acids 
thus  obtained  being  removed  by  shaking  the  liquid  with  ether  ;  the  solvent 
is  then  evaporated  and  the  residue  dried  at  100°  and  weighed. 

This  method  gives  only  approximately  exact  results,  which  are  more  accurate 
with  the  volumetric  than  with  the  gravimetric  method.  Modifications  have 
been  suggested  by  Fahrion  *  and  by  Wolff  and  Scholtze,2  but  it  is  most  commonly 
used  in  its  original  form.  For  more  exact  determinations,  the  method  of  Twitchell 
and  Gladding  may  be  used  under  the  conditions  laid  down  by  Holde  and  Mar- 
cusson.3  Another  method  for  the  determination  of  resin,  based  on  the  solu- 
bility of  the  alkali  resinates  in  acetone,  has  been  proposed  by  Leiste  and  Stiepel.4 


21.  Maumene  Number 

This  represents  the  rise  in  temperature 
produced  when  the  fatty  substance  is  mixed 
with  concentrated  sulphuric  acid  under 
definite  conditions.  Various  methods  of 
measuring  this  increase,  based  on  the  original 
one  of  Maumene,  have  been  suggested. 
Nowadays  suitable  forms  of  apparatus  are 
used  (thermo-oleometers) ,  such  as  that  of  Jean5 
or  that  of  Tortelli. 

Tortelli's  thermo-oleometer  consists  of  a 
small  glass  vacuum- jacketed  vessel  A  (Fig. 
57),  and  a  thermometer-stirrer  B  provided 
with  two  glass  vanes  near  the  bulb.  20  c.c. 
of  the  oil  are  pipetted  into  A,  stirred  for  a 
minute  by  rotation  of  the  stirrer  and  the  tem- 
perature read  (t).  By  means  of  another  pipette 
5  c.c.  of  sulphuric  acid  (D  exactly  1-8413)  are 
allowed  to  flow  on  to  the  oil  while  the  stirrer  is 
rotated  rapidly  backwards  and  forwards  and 
kept  just  in  contact  with  the  bottom  of  the 
vessel.  The  stirring  is  continued  until  the 


1  Chem.  Rev.  Fett.  Ind.,  1911,  p.  239. 


FIG.  57 


Chem.  Zeit.,  1914,  p.  369. 


8  Mitt.  aus.  dem  Kgl.  Materialpr.  Ami.,  1902,  p.  40. 

4  Chem.  Zentralbl.,  1914,  I,  p.  577. 

6  See  F.  Jean  :    Chimie  analytiqve  des  matures  grasses. 


392  FATTY  SUBSTANCES    (GENERAL  METHODS) 

temperature  reaches  a  maximum  (^)  and  remains  there  for  a  few  minutes. 
The  Maumene  number  is  t-^—t. 

To  obtain  constant  and  comparable  results  it  is  necessary  to  operate 
always  exactly  as  described  and  to  use  acid  of  the  exact  density  ;  this  may 
be  controlled  by  using  2oc.c.  of  distilled  water  in  place  of  the  oil,  the  value 
50  being  then  obtained  by  the  test.  The  oil  and  acid  used  must  be  left 
for  some  time  (about  30  minutes)  to  attain  the  temperature  of  the  surround- 
ing air. 

In  the  case  of  a  drying  oil,  it  is  convenient  to  dilute  the  oil  suitably 
with  olive  oil  of  a  known  Maumene  value,  the  result  obtained  being  then 
p  operly  corrected. 

Solid  fats  are  used  in  the  fused  state,  the  acid  being  at  the  ordinary 
temperature  ;  allowance  is  then  made  in  the  calculation  for  the  respective 
specific  heats. 

The  results  obtained  for  drying  and  non-drying  oils  with  Tortelli's  apparatus 
are  about  8-10  higher  than  those  given  by  Jean's  apparatus. 

The  results  vary  with  the  method  used  for  their  determination  and  with 
the  nature  of  the  substances  themselves.  In  general,  however,  drying  oils, 
fish  oils  and  fish-liver  oils  give  values  above  ico,  semi-  and  non-drying  oils 
and  blubber  oils,  values  less  than  100  (usually  30-90),  and  animal  fats  low  values 

(30-35)- 

Old  or  rancid  oils  and  those  which  have  been  exposed  to  the  air  or  heated 
give  values  different  from  the  fresh  oils. 


22.  Drying  Properties  of  Oils 

Certain  fixed  oils,  when  exposed  to  the  action  of  the  air,  thicken  and 
gradually  dry,  forming  transparent  and  elastic  pellicles  like  rubber.  Such 
oils  are  described  as  drying  oils.  Oils  which  either  remain  fluid  or  thicken  but 
little,  even  after  long  exposure  to  the  air,  are  non-drying  and  those  which 
thicken  and  dry,  although  incompletely  and  slowly,  are  termed  semi-drying. 

The  drying  properties  of  an  oil  depend  on  its  power  to  absorb,  with 
greater  or  less  rapidity,  atmospheric  oxygen,  so  that  the  drying  properties 
of  an  oil  may  be  determined  from  the  quantity  of  oxygen  absorbed  and 
from  the  rapidity  of  the  absorption. 

There  are  several  methods  of  determining  the  absorption,  the  most 
common  being  those  of  Livache  and  Bishop. 

1.  LIVACHE'S  METHOD.     Precipitated  lead  is  prepared  by  immersing  a 
sheet  of  zinc  in  10%  lead  acetate  solution  acidified  with  nitric  acid,  and 
washing  the  lead  precipitate  formed  with  water,  alcohol  and  ether  and  dry- 
ing it  in  a  vacuum  over  sulphuric  acid.     A  clock-glass  with  about  i  gram 
of  the  lead  on  it  is  weighed  and  about  0-5  gram  of  the  oil  allowed  to  fall 
in  drops  on  to  it,  care  being  taken  that  the  different  drops  do  not  unite. 
The  glass  is  re  weighed  and  then  exposed  to  the  air  in  a  well- ventilated  and 
lighted  place  at  a  constant  temperature.     It  is  weighed  from  time  to  time 
until  no  further  increase  occurs,  the  maximum  increase  representing  the 
oxygen  absorbed. 

2.  BISHOP'S  METHOD.     Pure  manganese  resinate  is  prepared  by  treating 
the  commercial  product  with  petroleum  ether,  filtering  the  solution,  dis- 


FATTY  SUBSTANCES    (GENERAL  METHODS)  393 

tilling  the  solvent,  drying  the  residue  on  a  water-bath  and  powdering  it. 
Of  this  resinate,  0-2  gram  is  heated  in  a  water-bath  with  10  grams  of  the 
oil  to  be  tested  until  completely  dissolved,  i  gram  of  precipitated  silica 
and  a  glass  stirring-rod  are  placed  in  a  dish  and  the  whole  tared,  1-02  gram  of 
the  oil  plus  resinate  being  allowed  to  fall  drop  by  drop  on  to  the  sand  and  the 
whole  weighed.  The  mass  is  well  mixed  and  left  exposed  to  the  air  at  the 
temperature  17-25°  for  drying  oils  or  20-30°  for  other  oils.  After  6  hours 
and  after  further  successive  intervals  of  12  hours  the  basin  is  weighed  (the 
mass  being  stirred  each  time)  until  of  constant  weight.  The  maximal 
increase  of  weight,  multiplied  by  160,  Bishop  terms  the  degree  oj  oxidation 
of  the  oil. 

Drying  oils  usually  absorb  oxygen  easily  and  rapidly,  so  that  after  an  expo- 
sure of  2-3  days  the  absorption  is  practically  at  the  maximum  attainable  even 
after  8-10  days.  On  the  other  hand,  non-drying  oils  do  not  increase  in  weight 
during  the  first  days  of  exposure  and  begin  to  absorb  a  small  quantity  of  oxygen 
only  after  5-6  days. 

According  to  Livache,  the  maximum  amount  of  oxygen  absorbed  per  100 
parts  of  linseed  oil  is  about  14,  the  amounts  for  walnut  oil,  poppy  seed  oil,  cotton- 
seed oil  and  beechnut  oil  being  8-5.  Olive,  arachis,  sesame  and  colza  oils  absorb 
only  1-3%  of  oxygen. 

According  to  Bishop's  method,  the  mean  degree  of  oxidation  is  17  for  lin- 
seed oil,  13-15  for  hempseed,  poppyseed  and  walnut  oils,  and  6-9  for  cotton- 
seed, sesame  and  arachis  oils. 

23.     Colour  Reactions. 

Different  fatty  substances,  more  particularly  the  fatty  oils,  give  special 
colorations  with  various,  reagents,  such  as  acids,  alkalies  and  different  salts. 
Some  of  these  reactions  serve  to  distinguish  certain  groups  of  oils,  whilst 
others,  being  specific  for  a  single  oil,  serve  to  characterise  the  latter.  These 
specific  reactions  will  be  dealt  with  in  the  special  part  in  the  paragraphs 
treating  of  the  particular  oils  (see  Cottonseed  Oil,  Sesame  Oil).  Some  of 
the  group  reactions  in  more  general  use  for  the  distinction  of  the  different 
groups  of  vegetable  oils  (for  animal  oils,  see  Fish  Oils)  will  be  described 
here. 

1.  HEYDENREICH'S  REACTION.     Five  or  six  drops  of  the  oil  are  allowed 
to  drop  from  a  pipette  on  to  about  5  c.c.  of  pure  sulphuric  acid  (66°  Baume) 
in  a  flat-bottomed  porcelain  dish.     In  about  three  minutes  the  oil  spreads 
to  form  a  very  thin  layer  on  the  acid ;  the  colour  formed  during  this  time 
in  the  zone  of  contact  between  oil  and  acid  is  observed. 

With  olive,  arachis  and  almond  oils,  there  is  no  sensible  change  of  colour, 
the  oil  remaining  pale  yellow  or  yellow,  although  sometimes  with  olive  oil 
a  greenish-yellow  coloration  appears.  With  very  old  or  rancid  oils,  colours 
tending  to  orange  or  brown  may  be  formed. 

Semi-drying  oils  give  orange  or  brown  colorations,  and  drying  oils  brown 
or  black  colorations,  while  the  oil  forms  a  thick  skin  (see  also  under  the 
separate  oils). 

2.  HAUCHECORNE'S  REACTION.    6  c.c.  of  the  oil  are  vigorously  shaken 
in  a  test-tube  with  2  c.c.  of  nitric  acid  prepared  from  3  vols.  of  pure  nitric 
acid  of  40°  Baume  and  i  vol.  of  water.     Note  is  made  of  the  coloration 


394  FATTY  SUBSTANCES   (GENERAL  METHODS) 

assumed  by  the  oil  after  shaking  for  about  two  minutes  and  of  its  colora- 
tion after  the  mixture  has  been  kept  for  20  minutes  in  a  boiling  water-bath. 

Olive,  almond,  hazel-nut  and  arachis  oils  retain  their  natural  colour 
or  become  somewhat  paler.  Olive  oil  may,  however,  sometimes  assume 
a  greenish  tint,  especially  in  the  cold.  If  these  oils  are  rancid,  they  may 
turn  orange-coloured. 

Sesame,  cottonseed,  beechnut,  linseed,  walnut,  colza,  and  mustard  oils, 
etc.,  change  to  orange  or  brownish  red. 

3.  BRULLE'S  REACTION.     In  a  test-tube  10  c.c.  of  the  oil,  o'i  gram  of 
dry,  finely  powdered  egg-albumin  and  2  c.c.  of  pure  nitric  acid  prepared 
as  for  Hauchecorne's  reaction  are  carefully  and  uniformly  heated  until  the 
acid  begins  to  boil,  the  whole  being  then  shaken  somewhat  and  the  heating 
continued  until  the  albumin  is  completely  dissolved,  this  occurring  in  a 
few  seconds. 

During  the  boiling  with  the  acid  and  albumin,  olive  oil  becomes  almost 
entirely  decolorised  and  after  cooling  forms  a  more  or  less  turbid  liquid  of 
a  straw-yellow  colour  which  persists  for  a  long  time,  but  after  24  hours  it 
sets  to  a  solid  mass  of  the  same  colour.  Similar  behaviour  is  shown  by 
arachis,  almond  and  walnut  oils. 

Seed-oils,  however,  become  deep  yellow  (colza,  sesame)  or  orange-red 
to  brown  (cottonseed,  poppyseed,  maize,  beechnut,  linseed,  etc.). 

4.  BELLIER'S  REACTION.    5  c.c.  of  the  oil  or  filtered   fused  fat,  5  c.r. 
of  pure,  colourless  nitric  acid  of  D  =  1-4  and  5  c.c.  of  a  cold,  saturated 
solution  of  resorcinol  in  benzene  are  introduced  into  a  graduated  cylinder 
with  a  ground  stopper  and  shaken  for  about  10  seconds,  the  colour  being 
observed  during  the  shaking  and  immediately  afterwards  (10-15  seconds). 

In  place  of  the  benzene  solution  of  resorcinol,  a  0-1%  ethereal  solution 
of  phloroglucinol  (Kreis)  may  be  used. 

Seed  oils  in  general,  and  especially  sesame,  cottonseed,  poppyseed, 
linseed,  maize  (corn  oil),  soja-bean  and  colza  oils,  give  colorations  varying 
from  pink  to  red  to  violet  to  brown  (with  phloroglucinol  more  distinctly 
red). 

This  reaction  serves  more  particularly  to  detect  vegetable  seed  oils  in  animal 
fats  (lard),  in  lard  oil,  in  foot  oils,  and  also  in  olive  oil,  since  these  animal  fats 
and  oils  and  olive  oil  give  no  appreciable  coloration,  at  any  rate  within  5-20 
seconds.  After  this  time  all  oils  and  fats  give  colorations. 

Practice  with  oils  and  fats  of  known  origin  is  necessary  in  order  to  distin- 
guish pure  oils  and  fats  from  mixtures  by  this  reaction. 

With  oils  which  have  been  subjected  to  long  exposure  to  light  or  to  heating 
in  the  air,  the  reaction  fails. 

24.     Elaidin  Test 

10  grams  of  the  oil  and  5  c.c.  of  nitric  acid  (D  1-40)  are  shaken  in  a  test- 
tube  for  two  minutes,  i  gram  of  mercury  being  then  added  and  dissolved 
by  energetic  shaking  ;  the  tube  is  then  left  at  rest  for  about  30  minutes. 

With  pure  olive  oil  a  solid  white  or  yellowish  mass  is  obtained  and  similar 
behaviour  is  shown  by  arachis,  almond  and  lard  oils.  Sheep's  foot  oils, 
and  mustard,  colza,  ravison,  sesame,  cottonseed  and  other  semi-drying 


SPECIAL  PART:   VEGETABLE  OILS  395 

oils  and  oils  of  marine  animals  give  a  more  or  less  semi-solid  or  pasty,  coloured 
mass.     Drying  oils  give  an  orange-ytllow  or  brown  liquid  product. 


SPECIAL  PART 
Vegetable  Oils 

By  vegetable  oils  is  meant  those  fatty  substances  extracted  from  the 
vegetable  kingdom  and  liquid  at  the  ordinary  temperature.  These  oils 
are  fairly  numerous  but  only  relatively  few  are  in  common  use,  these  includ- 
ing olive,  almond,  arachis,  colza,  cottonseed,  linseed,  sesame  and  castor 
oils,  which  are  treated  in  detail  below.  Table  XLIV  on  p.  410  gives  the 
principal  characters  of  these  oils  and  of  the  other  more  important  vegetable 
oils. 

ARACHIS  OIL 

From  the  seeds  of  Arachis  hypogcea.  It  is  pale  yellow  and  has  a  slight 
odour  and  an  agreeable  taste.  About  15  grams  dissolve  in  1000  c.c.  of 
absolute  alcohol  at  15°. 

With  Heydenreich's,  Brulle's  and  Hauchecorne's  reagents  it  gives  no 
appreciable  colorations,  only  a  pale  pink  colour  being  obtained  with  the 
last  in  the  cold.  The  other  chief  physical  and  chemical  characters  are  given 
later  in  Table  XLIV. 

Characteristic  of  arachis  oil  is  its  content  of  arachidic  and  lignoceric 
acids.  The  detection  and,  if  required,  the  determination  of  these  acids 
serves  to  identify  the  oil  and  to  detect  its  presence  (approximately  also 
the  quantity)  in  mixtures  with  other  oils. 

1.  Detection  and  Determination  of  Arachidic  and  Lignoceric 
Acids.— The  most  convenient  method  for  this  purpose  is  that  of  Tortelli 
and  Ruggeri  (see  below),  which,  like  various  other  methods,  is  based  on 
the  same  principle  as  Renard's  older  method.1 

A  preliminary  and  more  rapid  examination  may  be  made  by  the  other 
two  methods  described  below. 

i.  TORTELLI  AND  RUGGERI.  20  grams  of  the  oil  are  saponified, 
the  fatty  acids  separated,  and  the  solid  acids  extracted  from  these  by  means 
of  the  lead  salts,2  the  operations  being  carried  out  exactly  as  described  in 
general  method  18  (Tortelli  and  Ruggeri's  method).  The  solid  fatty  acids 
thus  obtained  are  placed  in  a  suitable  flask,  100  c.c.  of  90%  alcohol  and  a 
drop  of  dilute  hydrochloric  acid  (about  normal)  being  added.  The  flask 
is  closed  with  a  stopper  through  which  a  thermometer  passes  into  the  liquid 
and  is  then  heated  gently  (not  above  60°)  on  a  water-bath  and  carefully 

1  Among  other  methods  suggested  for  the  detection  of  arachis  oil  mention  may  be 
made  of  Torrini's  modification  of  Blarez's  method  (Ann.  Lab.  Mm.  centrale  Gabelle, 
Vol.  VI,  p.  513). 

2  According  to  Guarnieri,  the  preparation  of  the  lead  salts  may  be  shortened  by 
saponifying  the  oil  with  a  concentrated  solution  of  caustic  potash  in  glycerine  and 
then  precipitating  the  lead  salt  with  a  solution  of  lead  acetate  in  glycerine  (Staz.  sper. 
agr.  ital.,  1909,  p.  408). 


396 


ARACHIS  OIL 


shaken  until  a  clear  solution  is  obtained,  this  being  allowed  to  cool.  When 
the  temperature  has  fallen  somewhat,  slender  silvery  needles  begin  to  form 
and  rapidly  collect  into  tufts  (lignoceric  acid),  together  with  gradually 
increasing  shining,  nacreous  leaflets  (arachidic  acid).  With  the  fatty  acids 
from  pure  arachis  oil,  the  temperature  at  which  crystals  begin  to  form  as 
the  alcoholic  solution  cools  is  35-38°.  The  melting  point  of  the  mixture 
of  acids  obtained  in  this  first  crystallisation  is  usually  71-73°. 

No  other  oil  gives  a  crystalline  precipitate  in  such  conditions,  even 
when  the  alcoholic  solution  of  its  solid  acids  (prepared  as  above)  is  cooled 
to  the  ordinary  temperature.  Only  cottonseed  oil  and  some  olive  oil  from 
Tunisian  olives  give  a  precipitate,  but  this  is  amorphous  and  granular  and 
in  perfectly  opaque  mammillary  masses,  m.p.  below  70°  ;  further,  such 
precipitate  does  not  form  in  a  second  crystallisation. 

If  it  is  required  to  estimate  exactly  the  quantity  of  arachidic  and  lig- 
noceric acids,  the  crystals  formed  in  the  alcoholic  solution  are  collected 
and  washed  with  three  successive  quantities  of  10  c.c.  of  90%  alcohol  and 
then  thoroughly  with  70%  alcohol.  The  crystals  are  then  redissolved  in 
100  c.c.  of  90%  alcohol  (or  a  less  volume  if  the  amount  is  small)  and  the 
crystallisation  repeated  as  described  above.  The  crystals  thus  obtained 
are  collected  on  a  filter,  washed  twice  with  10  c.c.  of  90%  alcohol  and  then 
with  70%  alcohol  until  this  dissolves  no  more  ;  they  are  then  dissolved  in 
a  little  boiling  absolute  alcohol,  the  solution  being  evaporated  in  a  tared 
dish  and  the  residue  dried  at  100°  for  about  an  hour  and  weighed.1  To 
the  weight  found  is  added  that  of  the  arachidic  and  lignoceric  acids  remaining 
in  solution  in  the  90%  alcohol  used  for  the  various  crystallisations  and 
washings,  the  following  solubility  coefficients  (Tortelli  and  Ruggeri)  being 
employed  : 


Weight  of  Acid 
obtained  in  grams. 

Number  of  grams  dissolved  by  100  c.c.  of  90%  alcohol  at  a 
temperature  of 

15° 

17-5° 

20° 

i-oo  or  more 
0-70  . 

0-071 
.   0-068 
0-064 
0-052 
0-031 

0-081 
0-078 
0-075 
0-060 
0-040 

0-09I 
O-O89 
0-084 
O-O67 
0-045 

0-50  
0-25  
0-05  or  less 

Arachis  oil  contains,  on  the  average,  4-80%  of  arachidic  and  lignoceric  acids 
together,  so  that  the  proportion  of  these  acids  found  by  the  above  method 
indicates  if  the  oil  is  pure  or  not.  Further,  the  presence  and  quantity  of  these 
acids  serve  for  the  characterisation  and  determination  of  arachis  oil  in  mixtures 
with  olive  and  other  oils.  In  such  mixtures,  the  crystallisation  of  the  arachidic 
and  lignoceric  acids  from  the  alcoholic  solution  of  the  solid  fatty  acids  takes 
place  at  lower  and  lower  temperatures  as  the  proportion  of  arachis  oil  in  the 
mixture  diminishes. 


1  The  mixture  of  arachidic  and  lignoceric  acids  thus  obtained  should  melt  at  74- 


75-5 


ARACHIS  OIL  397 

The  content  of  arachis  oil  in  the  mixture  may  also  be  deduced  approximately 
from  the  temperature  at  which  the  first  crystals  form  : 

Temperature  of 
initial  precipi- 
tation .  .  35-38°  31-33°  28-30°  25-26°  22-24°  20-22°  18-20°  16-17° 

Proportion  of  ara- 
chis oil  .  .  100%  60%  50%  40%  30%  20%  10%  5% 

The  proportion  of  arachis  oil  in  a  mixture  may,  however,  be  determined 
more  exactly  from  the  quantitative  determination  of  the  arachidic  and  lig- 
noceric  acids,  the  content  in  the  pure  oil  being  4-80%.  In  this  way  as  little 
as  5%  °f  arachis  oil  in  admixture  with  other  oils  may  be  detected. 

2.  BELLIER'S  METHOD  (modified).1  Into  a  conical  flask  of  about  100 
c.c.  capacity  are  pipetted  i  c.c.  of  the  oil  and  5  c.c.  of  about  8%  alcoholic 
caustic  potash  solution  (80  grams  of  pure  potassium  hydroxide  dissolved 
in  80  c.c.  of  water  and  made  up  to  I  litre  with  90%  alcohol).  The  flask  is 
closed  with  a  stopper  carrying  a  tube  80  cm.  long  (to  avoid  loss  of  alcohol) 
and  heated  on  a  boiling  water-bath  with  continual  shaking  until  saponifi- 
cation  is  complete  (4-5  minutes).  The  liquid  is  then  cooled  to  about  25° 
and  shaken  with  1-5  c.c.  (exactly)  of  dilute  acetic  acid  (i  vol.  of  glacial 
acetic  acid  -f-  2  vols.  of  water),  3  drops  (not  more)  of  glacial  acetic  acid 
and  50  c.c.  of  70%  alcohol.  If  the  liquid  becomes  turbid  (as  usually  happens 
if  arachis  oil  is  present  in  marked  quantity),  it  is  gently  heated  until  clear, 
the  flask  being  then  closed  with  a  stopper  through  which  passes  a  ther- 
mometer with  its  bulb  in  the  liquid.  The  flask  is  then  cooled  and  shaken 
in  a  water-bath  so  that  the  temperature  of  the  liquid  becomes  exactly  16°, 
at  which  it  is  maintained  for  5  minutes  with  gentle  shaking. 

If  the  liquid  remains  clear  it  is  kept  at  15-5°  for  5  minutes,  and  if  it  still 
remains  clear,  arachis  oil  is  either  absent  or  present  in  less  proportion  than 
5%.  The  appearance  of  turbidity  at  15-5°  indicates  the  presence  of  arachis 
oil  (about  5%)  in  the  oil.  With  higher  proportions,  marked  turbidity 
occurs  even  at  16°.  With  pure  arachis  oil,  the  liquid  begins  to  show 
turbidity  at  about  40°. 

The  temperature  at  which  the  alcoholic  solution  of  the  fatty  acids,  obtained 
as  described  above,  first  becomes  turbid  serves  to  indicate  approximately  the 
proportion  of  arachis  oil  in  its  mixtures  with  olive  oil  : 

Temperature  at  which 

turbidity  appears. 
Pure  olive  oil         .......      ii-5-i4'5° 

-f-    5%  arachis  oil    .          .          .          .         16-17 

,,  10  ,,....         19-20 

,,         ,,  20  ,,....         25-26 

,,30  „  ...        29-30 

40  ,,  .        31-32 

..50  .        33-34 

60  „  .        35-36 

....  70  , 36-37 

80  „  .         38 

oo  .         39 

Pure  arachis  oil     .  .          .          .          .          .          .40 

1  The  modifications  of  Bellier's  original  method  (Ann.  de  Chim.  analyt.,  1899,  4) 
are  due  principally  to  Mansfeld  (Z.  Unt.  Nahr.  Genussm.,  1905,  XVII,  p.  57),  Adler 
(ibid.,  1912,  XXIII,  p.  676),  Luers  (ibid.,  1912,  XXIV,  p.  683),  and  Evers  (Analyst, 
1912,  p.  487). 


398  COLZA  OIL  AND   OTHER  CRUCIFEROUS   OILS 

3.  FACHINI  AND  DORTA'S  METHOD.1 — This  is  based  on  the  insolubility 
in  acetone  of  the  potassium  salts  of  the  solid  fatty  acids. 

10  grams  of  the  fatty  acids  obtained  from  the  oil  in  the  usual  way  are 
dissolved  in  90  c.c.  of  pure,  boiling  acetone,  the  boiling  solution  being 
treated  with  10  c.c.  of  aqueous  N-caustic  potash  solution  and  allowed  to 
cool  to  about  15°.  The  precipitate  formed  is  collected  on  a  dry  filter,  freed 
from  liquid  by  suction,  washed  with  small  portions  of  pure  acetone  and 
then  decomposed  with  a  dilute  acid  to  liberate  the  fatty  acids,  which  are 
dissolved  in  petroleum  ether.  The  solution  is  filtered  and  evaporated  and 
the  arachidic  and  lignoceric  acids  investigated  by  precipitation  from  90% 
alcohol  in  the  manner  of  the  Tortelli  and  Ruggeri  method. 

2.  Detection  of  Adulterations. — Commercial  arachis  oil  may  be 
adulterated  with,  or  may  contain  as  impurities,  sesame,  cottonseed,  colza, 
poppyseed  and  other  seed  oils.  Sesame  and  cottonseed  oils  are  detected 
by  the  reactions  of  Villavecchia  and  Fabris  and  of  Halphen  (see  Sesame 
Oil  and  Cottonseed  Oil),  colza  oil  by  Tortelli  and  Fortini's  reaction  and 
by  a  lowering  of  the  saponification  number  (see  Colza  Oil),  poppyseed  oil 
and  other  seed  oils  in  general  by  the  colour  reactions  of  Heydenreich, 
Hauchecorne,  and  Brulle,  and  by  a  diminution  in  the  content  of  arachidic 
and  lignoceric  acids. 

*  * 

Comestible  arachis  oil,  when  fresh,  should  contain  only  traces  of  free  acids. 
Old  oils  and  those  for  industrial  use  are  more  or  less  acid  and  may  contain  up 
to  about  30%  of  free  acid  (calculated  as  oleic  acid),  the  usual  proportion  being 
about  20%.  Arachis  oil  for  soapmaking  should  contain  not  more  than  i% 
of  moisture  and  foreign  matters  together  and  should  have  D  =0-919-0 -921, 
iodine  number  87-100,  solidification  point  of  the  fatty  acids  28-32-5°,  Maumene 
number  (Tortelli)  50-6. 

The  following  products  are  also  sold  :  Arachis  margarine,  produced  by 
pressing  the  oil  in  the  cold  (m.pt.  22-25°,  iodine  number  79-80),  arachis  grease, 
produced  by  purifying  the  rancid  oil  with  soda  and  composed  of  sodium  soap, 
neutral  oil  and  various  impurities  ;  and  arachis  oil  No.  2,  obtained  by  the  puri- 
fication of  rancid  oils  with  ammonia.  The  commercial  value  of  the  grease  and 
of  the  oil  No.  2  depends  on  the  content  of  total  fatty  matter  (see  General  Part, 
i,  A  and  C). 

COLZA  OIL  AND  OTHER  CRUCIFEROUS  OILS. 

The  more  common  oils  of  the  Cruciferge  are  colza  and  ravison  oils  ; 
less  common  are  those  of  jambo,  turnip,  mustard  (white  and  black),  radish 
seed  and  hedge  mustard.  All  have  very  similar  characters  and  properties. 

Colza  oil  and  ravison  oil  (from  the  seeds  of  Brassica  campestris  and  B. 
napus),  which  are  most  used,  are  yellow,  sometimes  tending  to  brown  ;  they 
have  a  special,  more  or  less  pronounced  odour  and  a  slightly  acid  taste. 
About  8  grams  dissolved  in  1000  c.c.  of  absolute  alcohol  at  15°.  Their 
characters  are  given  later  in  Table  XLIV. 

With  Heydenreich's  reagent  they  give  orange  colorations  with  fairly 
apparent  brown  striae,  especially  if  the  containing  dish  is  moved  slowly. 
With  Hauchecorne's  and  Brulle's  reagents  they  give  more  or  less  deep  orange 
colorations. 

1  Rend.  Soc.  chim.  ital.,  1910,  p.  248,  and  1912,  p.  51  ;   Chem,  Zeit.,  1914,  p.  18. 


COLZA  OIL  AND   OTHER  CRUCIFEROUS  OILS  399 

Characteristic  of  colza  andravison  oils,  and  of  those  of  the  other  Cruciferae 
mentioned  above,  are  their  low  saponification  number  (see  Table  XLIV) 
and  their  content  of  erucic  acid.  By  the  determination  of  the  saponification 
number  and  essentially  by  certain  tests  on  the  fatty  acids  these  oils  may 
be  identified  and  their  presence  in  mixtures  with  other  oils  detected.  These 
tests  are  as  follows.1 

1.  The  Tortelli  and  Fortini  Tests  on  the  Fatty  Acids.— These 
tests  include  the  determinations  of  the  melting  point  and  iodine  number  of 
the  solid  fatty  acids  and  the  critical  solubility  temperature  of  the  sodium 
soap  of  the  liquid  acids,  these  characters  being  especially  influenced  by 
the  presence  of  erucic  acid.  The  solid  and  liquid  fatty  acids  should  first 
be  prepared  (see  a)  and  the  determinations  indicated  then  made  (see  b  and  c). 

(a)  Preparation  of  the  solid  and  liquid  fatty  acids.     20  grams  of  the 
oil  are  saponified  with  alcoholic  potash  and  the  potassium  soap  converted 
into  the  lead  soap  by  the  Tortelli  and  Ruggeri  method  (see  General  Methods, 
18,  i).     The  lead  soap,  dried  with  filter-paper,  is  taken  up  with  80  c.c.  of 
ether,  shaken  well,  heated  for  20-30  minutes  in  a  reflux  apparatus  with 
occasional  shaking  and  then  cooled  in  water  at  15°  for  an  hour.     The  ethereal 
liquid  is  subsequently  decanted  through  a  filter  into  a  separating  funnel, 
as  little  as  possible  of  the  solid  residue  being  introduced  on  to  the  filter. 
The  residue  is  heated  with  40  c.c.  of  ether  in  a  reflux  apparatus  for  20  minutes, 
cooled  at  15°  for  an  hour,  and  the  whole  then  collected  on  the  filter,  the 
filtrate  passing  into  the  separating  funnel.     The  flask  and  residue  are  washed 
with  40  c.c.  of  ether.     This  washed  lead  soap,  insoluble  in  ether,  is  intro- 
duced into  another  separating  funnel  by  perforating  the  filter  and  washing 
down  with  ether,  of  which  100  c.c.  are  used. 

To  each  separating  funnel  150  c.c.  of  20%  hydrochloric  acid  are  added, 
the  funnel  being  thoroughly  shaken  and  then  left  at  rest  until  the  ethereal 
layer  has  separated  well,  the  aqueous  liquid  and  the  lead  chloride  formed 
being  run  off.  This  treatment  is  repeated  with  a  second  quantity  of  100 
c.c.  of  hydrochloric  acid  and  if  necessary  with  a  third  quantity.  The  two 
ethereal  solutions  are  then  washed  twice  with  100-150  c.c.  of  water,  care 
being  taken  not  to  shake  too  vigorously.  The  ethereal  solutions  are  finally 
filtered  through  two  pleated  filter-papers  into  two  glass  dishes,  from  which 
the  solvent  is  evaporated  at  as  low  a  temperature  as  possible.  In  one  dish 
the  solid  acids  (from  the  lead  salts  insoluble  in  ether)  and  in  the  other  the 
liquid  acids  of  the  oil  remain. 

(b)  Tests  on  the  solid  acids.     The  melting  point  is  determined  with  a 
bulb  tube  (see  General  Part,  4)  and  is  taken  as  that  temperature  at  which 
the  substance  falls  into  the  lower  part  of  the  bulb.     The  iodine  number  is 
determined  by  Hiibl's  method. 

The  solid  fatty  acids  of  pure  colza  oil  melt  at  41-42°  and  have  the  iodine 
number  62  :  those  of  other  seed  oils  and  of  olive  oil  melt  at  higher  temperatures 
and  have  lower  iodine  numbers  (see  later). 

(c)  Tests  on  the  liquid  acids.     The  sodium  soap  cf  these  is  prepared  and 

1  Use  may  also  be  made  with  advantage  of  Holde  and  Marcusson's  method  (Zeitschr. 
fur  angew.  Chem.,  1910,  p.  1260),  which  is  based  on  the  solubility  of  erucic  acid  in 
alcohol  at  a  low  temperature. 


400 


COLZA  OIL  AND   OTHER  CRUCIFEROUS  OILS 


its  critical  solubility  temperature  in  alcohol  determined.  For  this  purpose 
the  liquid  acids  are  dissolved  in  40  c.c.  of  absolute  alcohol,  the  solution 
being  heated  gently,  treated  with  slight  excess  of  saturated  sodium  car- 
bonate solution,  evaporated  almost  to  dryness  and  dried  in  a  vacuum  over 
sulphuric  acid.  The  dry  residue  is  powdered  and  purified  from  the  excess 
of  admixed  sodium  carbonate  by  successive  treatments  with  50,  40  and  30 
c.c.  of  absolute  alcohol,  with  which  it  is  heated  to  boiling  on  a  water-bath. 
The  liquids  are  filtered  hot  and  the  sodium  soap  separated  by  cooling  as 
a  white  or  straw-yellow,  caseous  mass,  which  is  pumped  off  and  dried  in  a 
vacuum  over  sulphuric  acid.  Of  the  perfectly  dry,  powdered  sodium  soap, 
0-5  gram  is  treated  in  a  large  test-tube  with  20  c.c.  of  absolute  alcohol,  the 
tube  being  hung  in  a  beaker  full  of  water  and  a  thermometer  introduced 
so  that  its  bulb  is  in  the  centre  of  the  liquid. 

The  liquid  is  then  heated  and  continually  stirred  with  the  thermometer 
until  a  clear  solution  is  obtained,  the  whole  being  then  allowed  to  cool  spon- 
taneously. At  a  certain  point  the  alcoholic  solution  in  the  test-tube  is 
seen  to  contain  minute  crystals,  which  are  only  barely  noticeable  at  first, 
but  rapidly  multiply  and  fill  the  whole  mass  of  the  liquid.  The  temperature 
at  which  the  first  crystals  are  observed  is  the  characteristic  critical  tem- 
perature. 

When  the  crystallisation  is  well  under  way,  the  thermometric  column 
remains  stationary  for  some  time,  or  at  least  falls  with  greatly  increased 
slowness. 

The  sodium  soap  of  the  liquid  fatty  acids  of  colza  oil  has  the  critical  solu- 
bility temperature  in  alcohol,  50-45°  ;  for  other  seed  oils  and  for  olive  oil  this 
temperature  is  lower  (see  later).  Further,  the  sodium  soaps  of  olive  oil  and 
of  various  seed  oils  are  deposited  with  a  caseous,  flocculent  and  glutinous  appear- 
ance, whereas  that  of  olive  oil,  at  least  at  first,  is  distinctly  crystalline. 

From  the  melting  point  and  iodine  number  of  the  solid  fatty  acids  and  the 
critical  solubility  temperature  of  the  sodium  soap  of  the  liquid  acids,  colza  (or 
ravison)  oil  may  be  detected  and  approximately  estimated  in  its  mixtures  with 
other  oils  ;  the  following  data  are  given  by  Tortelli  and  Fortini  : 


Critical  Solubility 

Melting  Point 

Iodine  Number 

Temperature  of 

Oils. 

of 

of 

the  Sodium  Soap 

Solid  Acids. 

Solid  Acids. 

of  the  Liquid 

Acids. 

Colza  oil       

41-42° 

62 

5^-45° 

Olive  oil       

58-59 

7-3 

24-20 

Colza  oil,  50  ) 

47-48 

32 

4O—  35 

Olive  oil,  50  j 

i  /         i 

D 

T         JJ 

Colza  oil,  30) 
Olive  oil,  70  j 

48-49 

28 

35-30 

Colza  oil,  20  1 

Olive  oil,  80  j 

50-51 

22 

35-30 

Colza  oil,  io| 

Olive  oil,  90  J 

54-55 

12-8 

34-30 

Sesame  oil  

55-56 

9-2 

20-18 

Arachis  oil  

57-58 

13 

22-18 

Cottonseed  oil  

57-58 

19 

16-14 

COTTONSEED   OIL  401 

2.  Detection  of  Adulterations. — Colza  and  ravison  oils  may  be  found 
mixed  with  olive  oil  (q.v.)  and,  in  their  turn,  may  be  adulterated  with  other 
seed  oils  (linseed,  poppyseed,  cameline,  hempseed,  etc.),  and  particularly 
with  fish  oils  and  oils  of  other  marine  animals,  as  well  as  with  mineral  oils 

The  determination  of  the  various  characters  (especially  saponification, 
iodine  and  Maumene  numbers)  and  the  test  for  erucic  acid  by  Tortelli  and 
Fortini's  method  readily  show  if  the  oil  is  pure  or  otherwise.  Seed  oils  in 
general  and  animal  oils  raise  the  saponification  number,  while  linseed,  hemp- 
seed  and  poppyseed  oils  raise  also  the  iodine  and  Maumene  numbers.  Fish 
oils  and  other  marine  animal  oils  are  detected  by  means  of  the  test  for  the 
octabromo-compounds  and  the  Tortelli  and  Jaffe  reaction  (see  Fish  Oils), 
and  mineral  oils  by  testing  for  unsaponifiable  substances. 

*  * 

Colza  oil  for  comestible  and  illuminating  purposes  should  be  well  refined  and 
not  acid.  Industrial  ravison  oil  should  have  :  D  =0-911-0-937,  iodine  number 
=  103-108,  saponification  number  =  175-178,  refractive  index  (Zeiss)  at  25° 
=  68-71,  Maumene  number  (Tortelli)  =  60-8°. 


COTTONSEED  OIL 

Obtained  from  the  seeds  of  Gossypium  herbaceum.  It  is  yellow  or  golden- 
yellow  or,  if  not  well  refined,  slightly  reddish-yellow  ;  it  has  characteristic 
but  not  very  pronounced  smell  and  taste.  About  18  grams  dissolve  in 
1000  c.c.  of  absolute  alcohol  at  15°.  The  other  physical  and  chemical 
characters  are  indicated  in  Table  XLIV. 

Heydenreich's  reagent  gives  a  deep  orange,  and  Hauchecorne's  or  Brulle's 
reagent  a  reddish-brown,  coloration  with  the  oil.  The  latter  also  gives 
the  following  characteristic  reactions  : 

1.  Milliau's  Reaction,  modified  by  Armani. — 10  grams  of  the  oil 
are  saponified  in  the  usual  way,  the  soap  being  dissolved  in  water  and  the 
solution  shaken  in  a  separating  funnel  with  100  c.c.  of  ether  and  30  c.c. 
of  10%  hydrochloric  acid.  After  standing,  the  acid  aqueous  layer  is  removed 
and  the  ethereal  solution  of  the  fatty  acids  washed  by  shaking  several  times 
with  water  until  the  latter  no  longer  gives  an  acid  reaction.  The  ether  is 
then  evaporated,  the  fatty  acids  thus  obtained  being  dissolved  in  15  c.c. 
of  90%  alcohol  (puriss.)  1  and  the  solution  mixed  with  1-2  c.c.  of  alcoholic 
silver  nitrate  solution  and  heated  in  a  water-bath  at  80-90°. 

Pure  cottonseed  oil  gives  an  intense  brown  coloration  almost  immediately 
and  then  also  a  black  precipitate.  Mixtures  of  oils  or  fats  containing  cotton- 
seed oil  yield  a  violet-brown  coloration  which,  after  a  few  minutes'  heating, 

1  This  reaction  and  in  general  all  reactions  with  silver  nitrate  require  the  use  of 
very  pure  alcohol,  which  does  not  show  the  least  brown  coloration  on  protracted  heating 
with  silver  nitrate.  The  absolute  alcohol  of  commerce  may  be  purified  as  follows 
(Tortelli  and  Ruggeri)  :  A  litre  of  alcohol  is  heated  for  an  hour  in  a  reflux  apparatus 
with  3  c.c.  of  5%  silver  nitrate  solution  and  then  distilled.  The  distillate  is  treated 
with  potassium  permanganate  until  it  assumes  a  persistent  red  colour  and  is  then  left 
for  24  hours  with  occasional  shaking  and  subsequently  filtered.  The  nitrate  is  treated 
with  2  grams  of  pure  caustic  potash,  heated  for  an  hour  in  a  reflux  apparatus  and 
distilled,  the  distillate  being  diluted  to  the  desired  strength  with  distilled  water. 

A.C.  26 


402  COTTONSEED   OIL 

becomes  intense  brown,  a  black  precipitate  also  forming  in  some  cases. 
Even  with  mixtures  containing  i%  of  cottonseed  oil  a  feeble  brown  colora- 
tion appears  after  5-10  minutes  of  heating,  whilst  with  oils  and  fats  free 
from  cottonseed  oil  no  sensible  coloration  is  ever  formed. 

2.  Milliau's   Reaction,   modified  by  Tortelli  and  Ruggeri. — The 
liquid  fatty  acids  are  extracted  from  20  grams  of  the  oil  by  Tortelli  and 
Ruggeri's  lead-salt  method  (see  General  Methods,  18,  i)  and  5  c.c.  of  them 
dissolved  in  a  test-tube  in  10  c.c.  of  90%  alcohol  (puriss.),  the  solution  being 
thoroughly  mixed  with  i  c.c.  of  5%  aqueous  silver  nitrate  solution  and 
heated  in  a  water-bath  at  70-80°. 

With  pure  cottonseed  oil  the  liquid  assumes  almost  immediately  a 
reddish  coloration  which  soon  turns  to  reddish-brown,  the  liquid  then  becom- 
ing turbid  and  appearing  violet-blue  in  transmitted  light ;  this  happens 
after  5—10  minutes  heating.  With  oils  and  fats  quite  free  from  cottonseed 
oil  no  coloration  is  obtained  even  after  heating  for  half  an  hour.  With 
mixtures  containing  only  i%  of  cottonseed  oil,  a  deep  brown  colour  soon 
appears. 

3.  Halphen's   Reaction. — According  to   the   most   recent  statement 
by  the  author,1  this  test  is  carried  out  as  follows  :   In  a  test-tube  are  placed 
I    c.c.    of   the    oil   and   2    c.c.    of    sulphocarbon    reagent    prepared    by 
dissolving^!  gram  of  powdered,  refined  sulphur  in  100  c.c.  of  carbon  disul- 
phide  and  then  diluting  with  100  c.c.  of  amyl  alcohol.     The  tube  is  immersed 
to  the  extent  of  two-thirds  in  a  salt  solution  and  heated  to  boiling  for  an 
hour,  2  c.c.  of  the  same  reagent  being  then  added  and  the  heating  continued 
for  30-40  minutes.     In  presence  of  cottonseed  oil,  a  red,  pink  or  orange- 
pink  coloration — according  to  the  proportion  of  cottonseed  oil  present 
(down  to  about  i%  as  a  minimum) — appears  more  or  less  rapidly. 

Water  hinders  the  reaction,  so  that  the  test-tube  should  be  thoroughly  dry 
and  the  reagents  and  oil  anhydrous  ;  the  latter  is  filtered  through  a  double 
dry  filter. 

Some  cottonseed  oils  which  have  undergone  special  treatments  give,  in 
place  of  a  decided  red  coloration,  a  brown  tint  with  an  orange  basis,  this  being 
well  seen  by  looking  through  the  whole  depth  of  the  liquid  at  a  white  ground. 

With  green  or  greenish  olive  oils  containing  little  cottonseed  oil,  the  reaction 
is  uncertain  ;  in  such  cases  it  is  well  to  decolorise  the  oil  beforehand  by  heating 
it  at  about  50°  with  animal  charcoal  and  filtering  at  the  same  temperature. 

4.  Halphen's  Reaction,  modified   by   Gastaldi.— A  test-tube  con- 
taining 5  c.c.  of  the  oil,  i  drop  of  pyridine  and  4  c.c.  of  a  i%  solution  of 
sulphur  in  carbon  disulphide  is  heated  in  a  boiling  water-bath  for  about 
30-60  minutes.     In  presence  of  cottonseed  oil  a  red,  pink  or  yellowish-pink 
coloration — according  to  the  amount  of  the  cottonseed  oil — is  formed  as 
with  Halphen's  reagent  ;  the  colour  is  more  distinct  and  intense  than  with 
the  latter  and  is  visible  even  with  0-5%  of  cottonseed  oil. 

*** 

Halphen's  reaction  and  Gastaldi's  modification  of  it  fail  with  cottonseed 
oils  which  have  been  heated  above  200°  or  subjected  to  prolonged  treatment 

1  G.   Halphen  :    Huiles  et  Graisses  vegetales  comestibles  (Paris,   1912),  p.  340. 


LINSEED   OIL 

with  sulphur  dioxide  or  chlorine  ;  the  reaction  of  the  liquid  fatty  acids  with 
silver  nitrate  (Tortelli  and  Ruggeri)  is  given,  although  in  an  attenuated  form, 
by  oils  which  have  been  heated  to  250°  for  10-20  minutes.  This  observation 
is,  however,  of  little  practical  value,  since  cottonseed  oil  treated  in  this  way 
is  scarcely  utilisable,  at  any  rate  for  mixing  with  comestible  olive  oil. 

It  is  also  to  be  noted  that  kapok  and  baobab  oils  give  the  same  reactions 
as  cottonseed  oil,  both  with  silver  nitrate  and  with  the  carbon  disulphide  re- 
agent, but  even  far  more  intensely  (with  silver  nitrate  the  reaction  occurs  even 
in  the  cold  and  with  Halphen's  reagent,  i%  of  kapok  oil  mixed  with  other  oil 
gives  almost  the  same  coloration  as  pure  cottonseed  oil).  Kapok  oil  may, 
according  to  Milliau,1  be  distinguished  from  cottonseed  oil  by  means  of  the 
action  of  silver  nitrate  on  the  fatty  acids  in  the  cold  ;  but  actually  the  fatty 
acids  of  cottonseed  oil  also  slowly  reduce  silver  nitrate  in  the  cold  and,  in  the 
case  of  mixtures,  the  reaction  may  be  due  as  much  to  a  little  kapok  oil  as  to 
a  large  amount  of  cottonseed  oil.  For  a  more  certain  indication  other  data 
must  be  employed.  For  instance,  with  mixtures  of  olive  and  arachis  oils,  the 
iodine  number  and  other  constants  will  show  if  the  proportion  of  the  extraneous 
oil  is  large  or  small.  Thus,  an  arachis  oil  which  gives  Halphen's  reaction  as 
sharply  and  intensely  as  pure  cottonseed  oil  but  has  a  normal  iodine  number 
and  a  normal  content  of  arachidic  and  lignoceric  acids  cannot  possibly  contain 
an  amount  of  cottonseed  oil  capable  of  giving  such  an  intense  colour  reaction  ; 
it  is,  therefore,  more  probable  that  such  an  oil  is  contaminated  with  a  little 
kapok  oil  than  with  much  cottonseed  oil. 


Comestible  cottonseed  oil  should  show  little  colour  and  no  unpleasant  smell 
or  taste  and  no  acidity.  The  industrial  oil  should  have:  D  =0-922-0-930, 
iodine  number  =  103-110,  solidification  point  of  the  fatty  acids  =  32-40°, 
Maumene  number  (Tortelli)  =  78-8°. 

Refinery  residues  of  cottonseed  oil  (soapstock),  which  are  pasty  and  brownish- 
yellow  to  black,  are  valued  on  the  basis  of  their  total  content  of  fatty  matter 
(standard  50%),  for  the  determination  of  which,  see  General  Part,  i,  A-C. 

Cottonseed  margarine  or  stearine  is  the  solid  part  which  separates  on  cooling 
the  oil  and  is  recovered  from  the  latter  by  pressure  at  10-11°  ;  it  is  white  or 
yellowish,  has  the  consistency  of  butter  (m.p.  16-32°)  and  gives  the  same  colour 
reactions  as  cottonseed  oil.  Its  specific  gravity  at  100°  is  0-864-0-868,  saponi- 
ncation  number  194-195,  iodine  number  95-96.  Its  value  depends  on  the 
titer  (solidifying  point  of  the  fatty  acids  ;  see  Tallow)  and  on  the  content  of 
total  fatty  matter  (see  General  Part,  i,  A-C}. 


LINSEED    OIL 

Ordinary  or  crude  linseed  oil  (for  boiled  linseed  oil,  see  next  chapter : 
Industrial  Products  of  the  Treatment  of  Fatty  Matters),  from  the  seeds  of 
Linum  usitatissimum,  is  yellow  or  brownish-yellow  and  has  a  peculiar  odour 
and  an  unpleasant  taste.  It  dissolves  in  about  40  parts  of  cold  or  5  parts 
of  boiling  absolute  alcohol.  It  contains  a  certain  quantity  of  unsaponifiable 
substances  (1-1-3%).  Its  physical  and  chemical  characters  are  given  in 
Table  XLIV. 

It  is  coloured  deep  orange  with  brown  striae  by  Heydenreich's  reagent 
and  soon  sets  to  a  black,  tarry  skin.  By  Hauchecorne's  or  Brulle's  reagent 
it  is  coloured  an  intense  brownish-red.  Besides  determinations  of  the 

*  Ann.  de  chim.  analyt.,  1905,  p.  9, 


404  LINSEED   OIL 

chemical  and  physical  characters,  the  following  special  tests  may  be  made 
on  this  oil : 

1.  Reaction    of    the    Hexabro  mo -compounds. — When    vigorously 
shaken  in  a  stoppered  cylinder  with  100  c.c.  of  a  mixture  of  28  vols.  of  glacial 
acetic  acid,  4  vols.  of  nitrobenzene  and  i  vol.  of  bromine  (Halphen's  bromine 
reagent],  5  c.c.  of  the  oil  give  a  yellow  precipitate  composed  of  hexabromo- 
compounds  of  linolenic  acid.     This  precipitate  is  soluble  in  boiling  benzene 
and  melts  undecomposed  at  175-180°  (difference  from  oils  of  marine  animals  ; 
see  Fish  Oils). 

Drying  walnut  and  hempseed  oils  behave  like  linseed  oil,  but  other 
vegetable  and  animal  oils  (excepting  those  of  marine  animals)  give  no 
precipitate  or  only  a  slight  turbidity  with  the  bromine  reagent. 

2.  Drying  Properties. — Linseed  oil,  being  a  drying  oil,  readily  absorbs 
oxygen,  its  drying  power  increasing  with  the  rapidity  with  which  it  absorbs 
its  maximum  proportion  of  oxygen.     Under  the  conditions  of  Livache's 
method  (see  General  Methods,  22,  Drying  Properties  of  Oils),  a  good  linseed 
oil  absorbs  about  14%  of  oxygen  in  two  days,  while  by  Bishop's  method, 
the  maximum  is  17%  and  is  reached  in  24  hours. 

3.  Detection    of    Adulterations. — Linseed    oil   may   be    adulterated 
with  other  vegetable  oils  (especially  colza,  cottonseed,  sesame,  poppyseed, 
cameline,  hempseed  and  other  drying  oils)  or  with  animal,  mineral  or  resin 
oils,  which  are  tested  for  as  follows  : 

1.  OTHER  VEGETABLE  OILS.     Marked  addition  of  other  vegetable  oils 
(especially  if  non-drying)  to  linseed  oil  generally  lowers  the  iodine  number 
and  the  Maumene  number  and  a  linseed  oil  with  an  iodine  number  below 
165  and  a  Maumene  number  less  than  120°  is  to  be  suspected.     In  par- 
ticular, colza  oil  may  be  detected  by  the  Tortelli  and  Fortini  test,  cotton- 
seed oil  by  the  Halphen  and  the  silver  nitrate  reactions,  and  sesame  oil 
by  the  furfural  reaction  (see  these  oils).     The  presence  of  drying  oils  (poppy- 
seed,  cameline  and  the  like)  is  moderately  difficult  to  ascertain,  since  these 
oils  do  not  possess  special  colour  reactions. 

2.  FISH  AND  OTHER  MARINE  ANIMAL  OILS.     The  presence  of  these  oils 
may  be  detected  by  the  Halphen  and  Marcusson  octabromo-compound 
test  and  the  Tortelli  and  Jaffe  colour  reaction  (see  Fish  Oils). 

3.  MINERAL  OILS.     These  are  detectable  by  the  fact  that  they  lower 
the  density,  the  iodine  number  and  the  saponification  number  of  linseed  oil  ; 
they  may,  in  addition,  be  tested  for  in  the  unsaponifiable  part  (see  General 
Methods,  19,  Unsaponifiable  Substances). 

4.  RESIN  OILS.     These  may  be  recognised  by  the  odour,  by  the  colour 
reaction  with  sulphuric  acid  (see  Resin  Oils)  and  by  the  rotatory  power 
(linseed  oil  is  almost  inactive,  whereas  resin  oils  are  decidedly  dextro- 
rotatory) ;    further,  they  increase  the  density  and  lower  the  iodine  and 
saponification  numbers. 

*** 

Free  acids  (calculated  as  oleic  acid)  up  to  7%  are  allowable  in  linseed  oil, 
unsaponifiable  substances  up  to  1-5%,  and  moisture  and  various  other  impurities 
up  to  i%.  For  the  genuine  oil,  D  =0-930-0-934,  iodine  number  =  164-191, 
Zeiss  refractometric  degree  at  25°  =  87-5,  solidification  point  of  the  fatty  acids 
=  13-3-20-6°. 


ALMOND  OIL  405 

ALMOND    OIL 

This  is  obtained  from  the  seeds  of  Amygdalus  communis  or  ordinary 
almonds,  the  sweet  and  bitter  varieties  giving  oils  very  similar  in  all  their 
properties.  Almond  oil  is  yellow  or  golden-yellow  and  about  16  grams  of 
it  dissolve  in  1000  c.c.  of  absolute  alcohol. 

With  Heydenreich's,  Hauchecorne's  and  Brulte's  reagents  L  remains 
pale  yellow  or  becomes  somewhat  paler.  The  characters  of  the  oil  are 
given  in  Table  XLIV  and  are  determined  by  the  methods  already  described. 

Detection  of  Adulterations. — Almond  oil  may  be  adulterated  with 
various  seed  oils  (arachis,  colza,  cottonseed,  walnut,  sesame",  etc.),  but 
especially  with  peach-kernel,  apricot-kernel  and  plum-kernel  oils.  To 
detect  such  admixtures,  the  various  characters  must  be  determined  (especi- 
ally solidifying  points  of  the  oil  and  of  the  fatty  acids,  saponification  and 
iodine  numbers,  Maumene  number)  and  certain  colour  tests  made  (see 
below,  2). 

The  different  extraneous  oils  may  be  detected  as  follows  : 

1.  ARACHIS,  SESAME,  COTTONSEED,  COLZA,  ETC.    The  first  is  detected 
by  the  arachidic  and  lignoceric  acids,  the  second  by  the  furfural  reaction, 
the  third  by  the  Halphen  reaction,  and  colza  oil  by  tests  on  the  fatty  acids 
(see  the  respective  oils).     The  presence  of  other  seed  oils  in  general  (exclud- 
ing those  dealt  with  in  2)  may  be  recognised  by  the  colour  reactions  of 
Heydenreich,  Hauchecorne,  Brulle  and  Bellier  (see  General  Methods,  23), 
to  which  almond  oil  does  not  sensibly  respond. 

2.  PEACH- KERNEL,  APRICOT- KERNEL  AND  PLUM- KERNEL  OlLS.   These 

oils  are  commonly  used  as  adulterants  or  substitutes  for  almond  oil.  They 
do  not  alter  the  characters  of  almond  oil  appreciably,  excepting  that  apricot- 
kernel  oil  somewhat  increases  the  Maumene  number  (50-51  for  almond  oil 
and  60-70°  for  apricot-kernel  oil).  The  two  following  reactions  serve  for 
their  detection. 

Bieber's  reaction.  Equal  volumes  of  pure  sulphuric  acid  of  66°  Baume, 
concentrated  nitric  acid  (D  1-42)  and  water  are  mixed,  one  vol.  of  such 
mixture  being  then  shaken  with  5  vols.  of  the  oil  in  the  cold.  Pure  almond 
oil  forms  a  yellowish  emulsion  which  becomes  reddish  only  after  some  time. 
Apricot-,  peach-  and  plum-kernel  oils  form  emulsions  of  a  transient  purple 
colour,  which  soon  changes  to  deep  orange  and  then  to  brown. 

Reaction  with  nitric  acid.  I  c.c.  of  fuming  nitric  acid,  I  c.c.  of  water 
and  2  c.c.  of  the  oil  are  shaken  vigorously  at  a  temperature  of  about  10°  : 
pure  almond  oil  yields  a  whitish  emulsion  which,  in  two  or  at  most  six 
hours,  sets  to  a  solid  mass  of  compact  white  granules  with  a  little  colour- 
less, supernatant  liquid.  In  presence  _of  apricot-  or  peach- kernel  oil  the 
emulsion  becomes  coloured,  almost  immediately,  more  or  less  reddish. 
If  the  solid  mass  and  the  liquid  turn  brown,  the  presence  of  other  extraneous 
oils  (colza)  is  demonstrated. 


*** 


For  medicinal  uses,  pharmacopoeias  prescribe  the  oil  obtained  by  pressure 
from  sweet  almonds. 

The  Official  Italian  Pharmacopoeia  requires  sweet  almond  oil  to  be  clear. 


406  OLIVE  OIL 

highly  mobile,  yellow,  almost  odourless,  and  of  sweetish  taste  :  it  should  have 
D  =  0-914— 0-920,  iodine  number  =  94-100,  saponification  number  =  190-195, 
and  should  be  incongealable  at  —  10°  and  should  respond  to  the  above  reaction 
with  nitric  acid. 


OLIVE    OIL 

This  is  obtained  from  the  fruit  of  Olea  europea,  and  is  pale  yellow  or 
sometimes  greenish  and  with  characteristic  smell  and  taste  ;  about  15 
grams  of  the  oil  dissolve  in  1000  c.c.  of  absolute  alcohol  at  13-15°. 

With  Heydenreich's,  Hauchecorne's,  Brulle's  or  Bellier's  reagent  it 
gives  a  pale-yellow  or  greenish  coloration,  excepting  with  very  old  and 
rancid  oils,  which  yield  more  or  less  deep  orange  tints.  The  characters  of 
the  oil  are  given  in  Table  XLIV. 

Olive  oil  may  be  adulterated  with  various  seed  oils,  especially  with 
arachis,  cottonseed,  sesame,  colza,  ravison  or  soja-bean  oil,  and  less  frequently 
with  maize,  poppyseed  and  other  oils.  Adulteration  with  lard  oil  and  with 
mineral  oils  has  been  observed,  but  only  in  exceptional  cases. 

1.  Tests  and  Determinations. — -Analysis  of  olive  oil,  with  the  aim 
of  ascertaining  the  quality  and  purity,  includes  mainly  the  following  : 

(a)  Examination  of  the  objective  properties,  that  is,  the  aspect  (lim- 
pidity), colour,  smell  and  taste.     The  odour  is  brought  out  well  by  rubbing 
a  few  drops  of  the  oil  between  the  hands  and  smelling  the  latter.     The 
odour  and  taste  indicate  the  fineness  of  an  oil,  its  state  of  preservation  and, 
with  much  practice,  its  purity. 

(b)  Determinations  :    solidifying  point  of  the  oil  and  the  melting  and 
solidifying  points  of  its  fatty  acids  ;    the  specific  gravity  ;    the  refraction 
on  the  Zeiss  butyro-refractometer  at  25°  ;    the  Maumene  number ;    the 
acid,  saponification  and  iodine  numbers.     All  these  are  made  by  the  methods 
described  in  the  general  part  of  the  present  chapter  (excepting  the  butyro- 
refractometer  reading,  for  which  see  Butter,  Vol.  II). 

(c)  Elaidin  test  (see  General  Methods,  24). 

(d)  The  arachidic  and  lignoceric  acid  test  and  the  Tortelli  and  Fortini 
tests  for  erucic  acid  (see  Arachis  Oil  and  Colza  Oil). 

(e)  The  colour  reactions  of  Heydenreich,  Hauchecorne,  Brulle,  Bellier, 
Milliau,  Halphen,  and  Villavecchia  and  Fabris  (see  General  Methods,  23  ; 
also  Cottonseed  Oil  and  Sesame  Oil). 

(/)  With  industrial  olive  oils,  determinations  of  the  moisture  and  ex- 
traneous impurities  are  necessary  (see  General  Methods,  i),  and  it  is 
sometimes  required  to  ascertain  if  the  oil  has  been  extracted  with  carbon 
disulphide  (see  later,  8). 

2.  Detection  of  Extraneous   Oils. — The  various  foreign  oils  which 
may  be  mixed  with  olive  oil  are  detected  as  follows  : 

1.  ARACHIS  OIL  :    by  the  presence  of  arachidic  and  lignoceric  acids, 
the  quantity  of  which  gives  an  approximate  measure  of  the  amount  of  the 
oil  (see  Arachis  Oil). 

2.  COLZA  OR  RAVISON  OIL  :   by  the  Tortelli  and  Fortini  test  (see  Colza. 
Oil).     In  considerable  proportion  it  lowers  the  melting  and  solidifying  points 


OLIVE  OIL  407 

of  the  fatty  acids  and  the  saponification  number  and  raises  the  Maumene 
number  and  refractometric  value  of  olive  oil. 

3.  COTTONSEED  OIL  :  by  the  reactions  of  Halphen  and  Milliau  (modified 
by  Armani  and  by  Tortelli  and  Ruggeri)   (see  Cottonseed  Oil).     Further 
it  raises  the  specific  gravity,  the  melting  and  solidifying  points  of  the  fatty 
acids,  the  Maumene  number,  the  refractometric  value  and  the  iodine  number. 

4.  SESAME  OIL  :    by  the  Villavecchia  and  Fabris  reaction  (see  Sesame 
Oil)  ;  it  alters  the  different  characters  in  the  same  sense  as  does  cottonseed 
oil. 

5.  OTHER  SEED  OILS  IN  GENERAL  :    by  the  general  colour  reactions 
already  indicated  (see  e,  above)  and  by  certain  alterations  in  the  characters 
of  the  oil. 

6.  ANIMAL  OILS  :  by  the  smell  and  by  testing  for  cholesterol  as  indicated 
for  tallow  (olive  oil  scarcely  contains  traces  of  phytosterol).     Fish  oils  and 
oils  of  other  marine  animals  are  detected  by  the  Tortelli  and  Jaffe  reaction 
(see  Fish  Oils). 

7.  MINERAL  OILS  :    by  the  lowering  of  the  saponification  number  and 
by  examination  of  the  unsaponifiable  part  (see  General  Methods,  19). 

3.  Detection  of  Sulphocarbon  Oil. — 200  grams  of  the  oil  are 
vigorously  shaken  with  50  c.c.  of  90%  alcohol  and  distilled  from  a  water- 
bath,  the  distillate  being  collected  in  a  flask  containing  a  few  c.c.  of  alcoholic 
caustic  potash  solution  (i  :  10)  (recently  prepared  from  the  purest  alcohol) 
and  immersed  in  cold  water.  When  about  two-thirds  of  the  alcohol  added 
to  the  oil  are  collected,  the  distillation  is  interrupted.  The  distillate  is 
faintly  acidified  with  dilute  acetic  acid  and  treated  with  1-2  drops  of  dilute 
copper  sulphate  solution  :  in  presence  of  potassium  xanthate  (formed  by 
the  action  of  the  carbon  disulphide,  distilled  with  alcohol,  on  the  alcoholic 
potash),  a  brown  coloration  is  formed  and  then  a  yellow  precipitate  of 
copper  xanthate.1  The  presence  of  carbon  disulphide  in  the  oil  is  hence 
concluded. 

* 
*  * 

Genuine  comestible  olive  oil  should  have  the  following  characters  : 

It  should  be  clear  and  have  the  normal  odour  and  taste. 

Solidifying  point :  it  should  begin  to  become  turbid  at  about  10°,  and  as 
a  rule  it  sets  to  a  semi-solid  mass  between  6°  and  2°  ;  at  o°  it  forms  a  soft  solid. 

Melting  point  of  the  fatty  acids  :    22-28°. 

Solidifying  point  of  the  fatty  acids  :    24-21  °. 

Specific  gravity  at  15°  :   0-914-0 -919. 

Reading  on  Zeiss  butyro-refractometer  at  25°  :  62-63.  With  oils  which  are 
defective  or  altered,  or  obtained  from  bad  olives,  or  washed  or  extracted  with 
carbon  disulphide,  the  reading  may  be  as  low  as  60. 

Maumene  number  (Tortelli)  :  41-47°  (44°  may  be  taken  as  the  mean).  With 
the  Jean  thermo-oleometer  :  32-39°. 

Acid  number  :    2  at  the  most. 

Saponification  number :    185-196  (normally  192-195). 

Iodine  number :  79-88.  Most  commonly  the  iodine  number  is  80-83,  only 
certain  oils  from  Liguria  and  Spain,  and  more  often  the  oils  of  Crete,  Tunis, 

1  Well  refined  sulphocarbon  oils  and  those  heated  for  an  hour  at  130°  no  longer 
give  the  above  reaction  or  any  other  reaction  specific  for  carbon  disulphide  or  other 
sulphur  compound. 


408  CASTOR  OIL 

Morocco  and  India,  have  a  higher  number  (85-88).  With  some  Moroccan  oils 
a  number  of  90  or  more  is  obtained,  but  such  cases  are  exceptional  and  some- 
times relate  to  oils  not  of  the  olive  but  of  the  fruits  of  the  Moroccan  olive 
(Arganum  sideroxylori),  a  tree  of  that  region  very  similar  to  the  olive.1 

Elaidin  test :    should  give  a  colourless  or  yellowish  solid  mass. 

Fatty  acid  test,  according  to  Tortelli  and  Fortini  :    negative  result. 

Colour  reactions  :  none  should  be  given,  either  with  the  general  reagents 
for  seed  oils  or  with  the  special  reagents  for  cottonseed,  sesame  and  marine 
animal  oils. 

In  general,  an  olive  oil  may  be  regarded  as  pure  when  :  it  is  coloured  only 
pale  yellow  by  Heydenreich's,  Hauchecorne's  or  Brulle's  reagent,  has  a  saponi- 
fication  number  not  less  than  192  and  an  iodine  number  not  exceeding  83,  and 
does  not  contain  arachidic,  lignoceric  or  erucic  acid.  An  oil  with  a  saponifi- 
cation  number  less  than  192  and  an  iodine  number  above  83 — within,  however, 
the  limits  indicated  in  Table  XLIV- — but  of  normal  behaviour  as  regards  all 
the  other  tests,  may  be  regarded  as  genuine. 

The  official  Italian  methods  give  for  olive  oil  the  limits  indicated  above 
for  the  different  characters,  excepting  that  the  solidifying  temperature  is  given 
as  2-6°,  the  refractometer  reading  at  25°  as  between  62  and  62-8,  and  the  iodine 
number  as  79-90.  They  give  further  :  Reichert-Meissl  number,  0-3  ;  Hehner 
number,  95-5-96-2  ;  acetyl  number,  4-10  ;  absolute  iodine  number,  95-104  ; 
unsaponifiable  residue,  which  should  be  constituted  of  minimum  traces  of 
phytosterol  scarcely  sufficient  for  the  reaction  with  chloroform  and  sulphuric 
acid  (100  grams  of  the  oil  yield  0-45-0-47  gram  of  crude  phytosterol,  whilst 
sesame  and  cottonseed  oils  give  respectively  1-28  and  1-20  gram). 

The  industrial  oil  for  lighting  or  lubrication  should  answer  the  requirements 
indicated  for  the  genuine  comestible  oil.  In  some  cases,  however,  admixtures 
of  seed  oils  (arachis,  colza  or  ravison)  are  allowed,  e.g.,  by  the  Italian  State 
Railways.  It  should  not  contain  more  than  i%  of  free  acid  (expressed  as 
monohydrated  sulphuric  acid),  should  not  congeal  above  —  5°,  should  not  be 
adulterated  with  animal,  mineral  or  resin  oils,  and  should  not  contain  muci- 
laginous substances  or  suspended  foreign  matters.  Further,  that  for  illumi- 
nating purposes  should  satisfy  definite  requirements  with  regard  to  the  mode 
of  burning,  the  illuminating  power,  etc. 

Industrial  olive  oil  for  soap-making  occurs  in  various  qualities  : 

Washed  oil,  obtained  by  washing  the  olive  residues  (sanse)  :  moisture  and 
impurities  up  to  2%  ;  free  from  sulphur  ;  acidity  variable  (10-40%  as  oleic 
acid) . 

Huile  lampante  (yellow  and  green),  obtained  by  filtering  the  washed  oil  : 
moisture  and  impurities  up  to  i%. 

Olive  oil  grease  or  residues  from  the  filtration  of  the  washed  oil :  should  be 
free  from  sulphur,  unbleached  and  not  treated  with  acid.  Its  value  depends 
on  its  content  in  total  fatty  matter — to  be  determined  directly — or  on  its  content 
in  fatty  acids  (exclusive  of  hydroxy-acids) — to  be  determined  by  saponifying 
the  grease  and  separating  the  total  fatty  acids. 

Sulphur  or  sulphocarbon  olive  oil,  which  is  distinguished  from  sanse  oil : 
saponification  number  not  less  than  180,  acidity  (as  oleic  acid)  up  to  65%, 
moisture  and  impurities  up  to  2%  and  hydroxy-acids  up  to  3%. 

CASTOR    OIL 

From  the  seeds  of  Ricinus  communis,  is  almost  colourless  or  yellowish, 
dense  and  viscous,  with  characteristic  smell  and  taste.  It  dissolves  in 
alcohol  in  all  proportions  and  in  acetic  acid  in  the  cold.  It  is,  however, 
almost  insoluble  in  petroleum  ether  and  in  vaseline  oil,  whilst  other  oils  are 

1  Zeitschr.  Unt.  Nahr.  Genussmittel,  1910,  II,  p.  749. 


CASTOR  OIL 


409 


soluble  in  these  solvents.  Its  physical  and  chemical  characters  are  given 
in  Table  XLIV. 

Castor  oil  Is  readily  distinguished  from  other  oils  by  its  solubility  in 
alcohol  and  its  insolubility  in  mineral  oils,  by  its  specific  gravity,  acetyl 
number,  viscosity  and  rotatory  power,  which  are  considerably  higher  than 
with  other  oils.  Its  viscosity  (Engler)  at  50°  is  about  16  (water  at  20  =  i) 
and  its  rotation  in  a  20  cm.  tube  at  the  ordinary  temperature  +  8°  to  +  9° 
(circular  degrees). 

When  prepared  recently  and^in  the  cold,  ic  is  neutral,  but  it  easily  becomes 
rancid.  Old  oils  and  those  extracted  in  the  hot  or  by  solvents  are  more  or 
less  acid  (up  to  more  than  20%  of  free  acids,  as  oleic  acid). 

The  following  tests  are  usually  made  : 

1.  Solubility. — This  serves  to  show  if  the  oil  is  pure  or  not,  and  is 
carried  out  as  follows  : 

(a)  Finkener's  test.     10  c.c.  of  the  oil  and  50  c.c.  of  90%  alcohol  are 
shaken  together  :  if  the  mixture  is  turbid  and  remains  so  at  20°,  the  castor 
oil  is  not  pure. 

(b)  Morpurgo's  test,     i  vol.  of  the  oil  and  3  vols.  of  oil  of  vaseline  are 
shaken  together  at  10-15° :    after  standing,  the  oil  of  vaseline  separates 
with  its  original  volume  if  the  castor  oil  is  pure,  but  with  an  increased 
volume  if  extraneous  oils  are  present.  i^i 

^2.  Detection  of  Adulterations.— (a)  VARIOUS  4  VEGETABLE  OILS. 
Castor  oil  is  rarely  adulterated  with  vegetable  oils  (cottonseed,  sesame, 
colza,  linseed,  etc.),  which  may  in  any  case  be  easily  detected,  since  they 
lower  the  specific  gravity,  acetyl  number  and  rotatory  power  and  raise 
the  saponification  number  (excepting  colza  or  ravison  oil). 

(b)  CROTON  ELLIOTIANUS  OIL.  This  oil  does  not  greatly  alter  the 
properties  and  is  difficult  to  detect,  especially  if  only  in  small  proportion. 
An  indication  of  its  presence  may,  however,  be  obtained  by  boiling  the 
oil  with  a  very  concentrated  potassium  hydroxide  solution :  on  cooling,  a 
white,  soapy  mass  is  obtained  with  pure  castor  oil,  and  a  yellow  or^brown 
mass  in  presence  of  croton  oil  (i%  or  more).1  ^ 

3.  Test  for  Resinous  Substances. — To  ascertain  if  a  sample  of  castor 
oil  is  contaminated  with  resinous  substances  or  has  been  extracted  in  the 
hot,  the  following  test,  prescribed  by  the  official  Italian_pharmacopceia,  is 
made.  3  c.c.  of  the  oil,  3  c.c.  of  carbon  disulphide  and  i  c.c.  of  cone. 
sulphuric  acid  are  shaken  together  for  some  minutes  :  the  mixture  should 
not  turn  brown. 

*** 

Medicinal  castor  oil,  according  to  the  official  Italian  pharmacopoeia,  should 
be  extracted  by  pressure  in  the  cold  from  husked,  peeled  seeds  ;  it  should  be 
clear,  almost  colourless  or  yellowish,  and  not  of  acrid  taste,  soluble  in  5  parts 
of  90%  alcohol  at  15°  and  in  2  parts  at  25°,  and  extremely  soluble  in  absolute 
alcohol,  ether  or  glacial  acetic  acid.  Its  iodine  number  should  be  80-85,  and 
its  saponification  number  180-182,  and  it  should  answer  to  the  reaction,  described 

1  Mazzucchelli  :  Detection  of  croton  oil  in  castor  oil  (Arch,  di  farm,  sper.,  i9°5t 
p.  223). 


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412  SESAME  OIL 

above,    with   carbon   disulphide    and   sulphuric   acid.     Freshly   prepared    and 
dissolved  in  alcohol,  it  should  have  no  acid  reaction. 

Castor  oil  for  industrial  purposes  (soap-making)  may  have  :  moisture  and 
impurities  up  to  i%  ;  0=0-960-0-974;  iodine  number,  82-86;  solidifying 
point,  —  10°  to  —  18°  ;  solidifying  point  of  the  fatty  acids  =  3°  ;  acetyl  number 
of  the  fatty  acids  =  153-4-156  ;  Maumene  number  (Tortelli)  =  67-8°. 


SESAME  OIL 

From  the  seeds  of  Sesamum  indicum  and  5.  orientate,  is  more  or  less 
deep  yellow,  of  faint  special  odour  and  pleasant  taste.  From  16  to  19 
grams  dissolve  in  1000  c.c.  of  absolute  alcohol  at  15°.  Its  characters  are 
given  in  Table  XLIV. 

With  Heydenreich's,  Hauchecorne's,  Bridle's  and  Bellier's  reagents  it 
gives  the  colorations  usual  for  seed  oils.  Characteristic  of  sesame  oil  is 
the  following  colour  reaction,  which  serves  to  detect  it  in  olive  oil  and  in 
all  other  oils  and  fats. 

1.  Villa  vecchia  and  Fabris  Reaction.1  —  Two  or  three  drops  of  alco- 
holic furfural  solution  (2  grams  of  furfural  in  100  c.c.  of  95%  alcohol)  2 
and  then  5-10  c.c.  of  the  oil  and  10  c.c.  of  pure  cone,  hydrochloric  acid 
(D  1-19)  are  poured  into  a  test-tube,  the  whole  being  well  shaken  for  a  few 
moments  and  then  left  to  stand.     The  acid,  coloured  dark  red,  soon  separates 
in  the  lower  part  of  the  tube  and  becomes  increasingly  dark,  while  the  upper 
oily  layer  represents  a  yellowish-red  emulsion.     The  coloration  is  clearly 
observable  even  with  mixtures  containing  only  0-5%  of  sesame  oil. 

No  other  oil  gives  such  a  reaction  ;  only  certain  olive  oils  (from  Tunis  and 
Algeria,  and  some  from  Bari,  Brindisi  and  Lecce)  may  yield  with  the  above 
reagent  a  pink  or  reddish  colour,  which  is,  however,  always  less  intense  than 
and  quite  different  in  tint  from  that  produced  by  sesame  oil.  In  doubtful  cases, 
the  reaction  may  be  carried  out  with  the  liquid  fatty  acids  separated  by  Tortelli 
and  Ruggeri's  method  (see  General  Methods,  18,  i). 

2.  Detection  of  Adulterations.  —  Sesame"  oil  may  be  adulterated  with 
drying  oils,  colza  oil  and  arachis  oil  :  the  first  raise  the  iodine  numbei  and 
the  Maumene  number,  while  the  others  are  detectable  by  testing  for  the 
arachidic  and  lignoceric  acids  and  by  the  Tortelli  and  Fortini  test  (see 
Arachis  Oil  and  Colza  Oil). 


Comestible  sesame  oil  should  be  clear,  of  normal  taste  and  odour,  and  not 
too  acid  (fresh  oil  may  contain  0-5-5%  °f  free  acids,  calculated  as  oleic  acid  ; 
old  oils  may  contain  as  much  as  35%). 

The  permissible  limits  for  the  industrial  oil  (for  soap-making)  are  :   moisture 

1  This  reaction  (see  Zeitschr.  fur  angew.  Chemie,  1892,  p.  509,  and  1893,  P-  5°5)  is 
due  to  the  action  of  furfural,  in  presence  of  cone,  hydrochloric  acid,  on  the  methylene 
ether   of    hydroxyhydroquin   onecontained  in  sesame  oil,  according  to  the  investiga- 
tions of  Malagnini  and  Armani  (see  Rend.  Soc.  chim.  di  Roma,  1907,  V,  p.  133).     It 
serves  as  a  rational  substitute  for  Bandouin's  reaction,  which  consisted  in  shaking  the 
oil  with  cone,  hydrochloric  acid  and  sugar.     In  Baudouin's  reagent  also  the  active 
principle  is  furfural,  which  is  formed  by  the  action  of  the  acid  on  the  saccharose,  but, 
this  formation  being  slow  and  limited,  Baudouin's  reaction  is  less  rapid  and  certain. 

2  The  furfural  should  be  pure  and  recently  distilled,  so  that  it  shows  little  colour, 


CACAO  BUTTER  413 

and  impurities,  up  to  1%  ;  D  =  0-920-0-924  ;  iodine  number  =  100-114  ; 
Maumene  number  (Tortelli)  =  71-3°  ;  solidifying  point  of  the  fatty  acids  = 
18-23-4°- 

Vegetable  Fats 

These  are  fatty  substances  of  vegetable  origin  and  solid  at  the  ordinary 
temperature.  Among  them  are  also  some  so-called  Vegetable  waxes,  such 
as  Japan  wax  and  myrtle  wax,  which  are,  however,  not  true  waxes  but  solid 
fats,  since  they  are  composed  of  glyceryl  esters  and  not  esters  of  higher 
alcohols.1  True  waxes  of  vegetable^origin  include  only  carnauba  wax  and 
a  few  others  (see  Waxes) .  ;  i 

The  more  important  vegetable  fats  are  those  of  cacao,  coco-nut,  palm 
and  palm-kernel,  vegetable  tallow  and  a  few  others  which  are  described  ; 
their  characters  are  given  in  Table  XLV,  together  with  those  of  other 
vegetable  fats  of  some  interest. 


CACAO    BUTTER 
(Cocoa  Butter) 

From  the  seeds  of  Theobroma  cacao,  is  a  somewhat  brittle,  yellowish- 
white  solid  with  a  taste  and  smell  recalling  those  of  torrefied  cacao.  It 
dissolves  in  5  parts  of  boiling  absolute  alcohol  and  is  almost  insoluble  in 
90%  alcohol ;  it  is  soluble  in  3  parts  of  ether.  It  does  not  readily  turn 
rancid,  and  only  when  very  old  or  badly  stored  does  it  contain  more  than 
i%  of  free  acid  (calculated  as  oleic  acid)  ;  the  rancid  fat  is  white.  Fat 
from  the  skins  of  cacao  seeds  is,  however,  markedly  acid  even  when  fresh. 
The  characters  of  the  fat  are  given  in  Table  XLV. 

Detection  of  Adulterations. — It  may  be  adulterated  with  coco-nut 
butter,  tallow,  stearine,  solid  paraffin  and  wax,  or,  more  rarely,  with  other 
vegetable  fats  (Japan  wax,  Dika  oil),  almond  oil,  hazelnut  oil  or  other  seed 
oils.  Such  adulterations  are  detected  by  determining  the  different  char- 
acters of  the  fat,  bearing  in  mind  the  following  : 

Coco-nut  oil  raises  the  saponification  number  and  the  volatile  acid 
number,  but  lowers  the  iodine  number  and  the  refractometric  reading. 
Stearine  raises  the  acid  number  and  lowers  the  iodine  number,  and  is,  more- 
over, easily  detectable  by  its  ready  solubility  in  alcohol.  Solid  paraffin 
and  wax  lower  the  saponification  number  and  the  iodine  number  and  may 
be  recognised  in  the  unsaponifiable  portion.  Vegetable  oils  in  general  lower 
the  specific  gravity  and  the  melting  point  and  raise  the  iodine  number  and 
the  refractometric  reading.  Japan  wax  increases  the  density,  the  acid 
number  and  the  saponification  number  and  lowers  the  iodine  number.  Dika 
oil  raises  the  saporiification  number  and  the  refractometric  value  and  lowers 
the  iodine  number  (see  Table  XLV).  Tallow  is  not  easily  detectable  by 
physical  and  chemical  characters  alone,  but  its  presence  may  be  shown 
by  the  cholesterol  test  (see  Lard). 

1  These  vegetable  waxes  are  distinguishable  from  true  waxes  in  that  they  are  com- 
pletely saponified  by  alcoholic  potash,  yielding  soaps  entirely  soluble  in  water. 


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415 


416  COCO-NUT  OIL— PALM  OIL 

For  testing  for  extraneous  fats  in  general,  recourse  may  also  be  had  to 
determinations  of  the  critical  solubility  temperature  in  absolute  alcohol 
and  in  glacial  acetic  acid  and  of  the  melting  points  of  glycerides  insoluble 
in  a  mixture  of  alcohol  and  ether,  as  suggested  by  Grimm.1 

* 

*  * 

Cacao  butter  is  to  be  regarded  as  genuine  when  its  physical  and  chemical 
characters  he  within  the  limits  indicated  in  Table  XLV  and  it  does  not  contain 
any  of  the  above-mentioned  impurities. 

It  should  be  noted  that  substitutes  for  cacao  butter  are  sold  under  various 
names,  e.g.,  chocolate  butter,  consisting  of  coco-nut  oil ;  cacao  butter  (coco-nut 
oil  and  Japan  wax).  The  so-called  Samana  cacao  butter  is  a  fat  which  melts 
at  about  12°  and  when  left  for  a  long  time  separates  a  liquid  part ;  it  has  D 
at  1 7-5°  =0-906,  refractometric  reading  at  40°  =  50-5  and  iodine  number 
=  53-59- 

COCO-NUT    OIL 

From  the  albumin  or  pulp  of  the  coco-nut,  fruit  of  Cocos  nucifera.  It  is 
white  or  pale  yellow,  and  has  the  consistency  of  butter  and  a  special  odour. 
In  coco-nut  butter  well  refined  for  comestible  use  this  odour  is  almost  entirely 
lacking,  but  boiling  with  a  little  alcohol  and  a  few  drops  of  cone,  sulphuric 
acid  brings  out  the  odour  distinctly. 

It  dissolves  in  2  vols.  of  absolute  alcohol  at  30°  and  in  2  vols.  of 
90%  alcohol  at  60°.  Its  physical  and  chemical  characters  are  given  in 
Table  XLV. 

With  Heydenreich's,  Hauchecorne's  or  Brulle's  reagent  it  gives  no 
sensible  coloration,  and  it  does  not  react  with  silver  nitrate  or  with  furfural 
and  hydrochloric  acid.  Characteristic  of  coco-nut  oil  are  the  rather  high 
saponification  number,  the  low  iodine  number  and  the  volatile  acid  number, 
which  is  greater  than  those  of  vegetable  oils  and  fats  in  general. 

* 

*  * 

Pure,  edible  coco-nut  oil  is  perfectly  white  (sometimes  dyed  yellowish  to 
imitate  butter),  odourless  and  neutral  or  almost  so  (acidity  number  not  beyond 
i%  as  oleic  acid)  and  has  a  fresh,  pleasant  taste. 

Industrial  coco-nut  oil  (for  soap)  is  white  or  faintly  yellow  and  has  a  more 
or  less  pronounced  taste  and  smell.  The  finest  and  whitest  quality  bears  the 
name  Cochin  neige,  while  the  others  are  called  White  Cochin,  Ceylon  and  Copra 
oils. 

The  allowable  limits  for  these  industrial  oils  are  :  acidity  (as  oleic  acid) 
up  to  4%  for  Cochin  and  up  to  10%  for  other  qualities  ;  moisture  and  foreign 
impurities,  up  to  i%  ;  m.pt.  =  20-28°,  setting  point  =  22-14°  •  titer  (setting 
point  of  the  fatty  acids)  =  16-23°  ;  volatile  acid  number  =  5-6-8-5  ;  saponi- 
fication number  =  248-260  ;  iodine  number  =  7-68-9-5. 


PALM    OIL 

From  the  flesh  of  the  fruit  of  the  oil-palm  (Elaeis  guineensis  and  E. 
melanococca) .  It  has  the  consistency  of  butter,  a  more  or  less  intense  yellow 
or  orange  colour  which  weakens  considerably  on  exposure  to  air  and  light, 
and  a  pleasant  smell  recalling  that  of  the  iris. 

1  Chem.  Rev.  Fett.-Ind.,  1914,  pp.  47  and  74. 


OTHER  VEGETABLE  FATS  417 

With  chloroform  and  sulphuric  acid  it  gives  a  reaction  similar  to  that 
of  cholesterol  (see  General  Methods,  19). 

Its  value  depends  essentially  on  the  content  of  moisture  and  foreign 
impurities  and  on  the  setting  point  of  the  fatty  acids  (titer).  These,  then, 
are  the  principal  determinations  made  (see  General  Methods,  i,  and  also 
Tallow)  ;  the  acid  saponificadon  number  is  also  measured  and  sometimes 
the  glycerine  content  (see  General  Methods). 

* 
*  * 

The  titer  of  palm  oil  generally  lies  between  40°  and  50°.  Its  content  of 
water  and  foreign  matters  varies  from  0-5%  to  17%,  but  with  a  good  specimen 
should  not  exceed  2%.  Commercial  palm  oil  is  always  markedly  acid  ;  when 
recently  prepared  the  oil  may  contain  about  10%  of  free  acids  (calculated  as 
palmitic  acid),  but  most  commercial  oils  show  20-50%,  while  certain  old  oils 
of  special  type  may  contain  nearly  90%.  As  a  rule  the  content  of  glycerine 
diminishes  as  the  free  acid  increases. 

The  best  commercial  oil  is  that  from  Lagos,  with  2%  of  moisture  and  im- 
purities at  most ;  minimum  titer,  43°  ;  acidity  usually  not  greater  than  20%  ; 
saponification  number,  196-207.  The  Benin  oil,  which  is  brown,  has  the  titer 
40-49°  and  acidity  up  to  50%. 


PALM-KERNEL    OIL 

From  the  seeds  of  the  oil-palm  (Elaeis  guineensis  and  E.  melanococca), 
It  has  the  consistency  of  butter,  is  white  or  yellowish,  has  a  special  odour 
similar  to  that  of  coco-nut  oil  and  readily  becomes  rancid.  In  all  its  pro- 
perties it  closely  resembles  coco-nut  oil  (see  Table  XLV),  from  which  it  is 
difficult  to  distinguish  it.  Analysis  of  this  oil  is  carried  out  like  that  of 

coco-nut  oil  (q.v.}. 

* 
*  * 

In  palm-kernel  oil  for  industrial  purposes  up  to  i  %  of  moisture  and  ex- 
traneous impurities  are  allowed  and  up  to  10%  of  free  acids  ;  saponification 
number  =  241-250  ;  volatile  acid  number  =  4-8-5-6  ;  titer  =  20-5-25-5°. 


OTHER    VEGETABLE    FATS 

Of  the  other  vegetable  fats  the  following  are  commonly  known  and  used  : 

Vegetable  Tallow  or  Chinese  Tallow  (Stillingia  fat],  from  the  seeds 
of  StUlingia  sebifera.  Its  characters  and  properties  may  vary  with  the 
method  of  extraction,  but  it  is  usually  solid,  hard  and  white  outside  and 
more  or  less  stained  with  earthy  and  vegetable  residues,  yellowish  inside, 
and  odourless,  or  almost  so. 

Illipe-nut  Butter,  Fat  or  Oil  (Mahwa  fat),  from  the  seeds  of  Bassia 
latifolia.  It  has  a  tallowy  consistency,  a  yellowish  or  greenish  colour  and 
a  slight  aromatic  odour,  and  readily  turns  rancid. 

Mowrah  Butter,  Fat  or  Oil,  from  the  seeds  of  Bassia  longifolia  ;  of 
tallowy  consistency,  yellowish  colour  when  fresh,  rather  bitter  taste,  and 
odour  recalling  that  of  cacao  seeds  ;  it  easily  becomes  rancid  and  decolorised. 

The  analysis  of  these,  as  of  any  other  vegetable  fat,  comprises  deter- 
minations of  moisture  and  foreign  impurities,  titer,  acidity  and  saponirica- 
A.c.  21 


4i8  ANIMAL  FATS— TALLOW 

tion  numbers,  and  any  other  characters  which  may  serve  to  establish  its 
origin  (see  Table  XLV). 

Animal  Fats 

The  most  important  animal  fats  are  :  butter,  dealt  with  in  the  chapter 
on  milk  and  its  products  (see  Vol.  II,  Chapter  II),  tallow,  lard,  bone-fat 
and  the  foot-oils,  which  are  considered  below  in  detail ;  a  large  number 
of  other  fats  are  obtained  from  different  animals,  but  few  are  of  importance. 
The  characters  of  these  are  given  in  Table  XLVII. 

So-called  wool  fat,  which  from  its  composition  is  to  be  regarded  as  a 
wax,  is  dealt  with  in  the  article  on  waxes. 


TALLOW 

This  is  a  fat  obtained  from  bovine  (ox-tallow)  and  from  ovine  animals 
(sheep's  or  goat's  fat).  It  is  stiff  and  yellowish  and  has  a  characteristic 
smell ;  in  the  light  and  air  it  rapidly  becomes  rancid  and  decolorised.  One 
part  of  it  dissolves  in  40  parts  of  94%  alcohol.  Its  physical  and  chemical 
characters  are  given  in  Table  XLVII. 

Its  analysis  includes  firstly  the  determination  of  the  titer  (solidifying 
point  of  the  fatty  acids),  on  which  depends  the  commercial  value  (see  i). 
Determinations  are  also  to  be  made  of  the  water  and  foreign  impurities, 
of  the  acid  and  saponification  numbers  and,  sometimes,  of  the  glycerine 
(see  General  Methods).  Any  adulteration  with  bone  fat,  wool  fat,  palm  oil 
or  coco-nut  oil,  may  be  detected  as  described  below  (2). 

1.  Titer  Test. — The  sample  for  this  determination  must  be  taken 
carefully,  portions  being  taken  from  each  cake  or  cask  (at  different  points) 
of  the  bulk  and  these  melted  together  at  a  temperature  not  exceeding  60° 
and  the  fused  mass  continually  stirred  until  it  reaches  the  ordinary  tem- 
perature. 

50  grams  of  this  sample  are  saponified  with  40  c.c.  of  caustic  potash 
solution  (D  1-4)  and  40  c.c.  of  96%  alcohol.  The  soap  is  dissolved  in  a 
litre  of  water  and  boiled  in  a  dish  to]expel  the  alcohol,  the  fatty  acids  being 
then  separated  by  means  of  a  slight  excess  of  dilute  sulphuric  acid  and  the 
boiling  continued  until  these  acids  form  a  perfectly  limpid  layer  free  from 
suspended  clots.  The  aqueous  liquid  is  siphoned  off  and  the  acids  washed 
with  hot  water  until  they  no  longer  give  an  acid  reaction  with  methyl  orange 
and  then  solidified  by  cooling.  The  disc  of  solid  acids  is  melted  on  the 
water-bath,  filtered  through  a  dry  filter  in  a  boiling  water-oven  and  the 
filtrate  left  overnight  in  a  desiccator. 

The  setting  point  of  the  fatty  acids  thus  obtained  is  ascertained  as 
follows  :  A  test-tube  b  (see  Fig.  58)  about  15  cm.  long  and  2  cm.  internal 
diameter  is  filled  to  about  two-thirds  with  the  acids  (about  30  grams)  and 
heated  in  a  water-bath  until  most  of  the  substance  is  melted  ;  the  tube  is 
then  removed  from  the  bath  and  the  mass  stirred  with  a  glass  rod  until 
completely  liquid  (heating,  if  necessary,  for  a  few  moments).  The  tube  is 
then  fitted  through  the  hole  of  the  stopper  d  of  a  fairly  wide  glass  cylinder 


TALLOW 


419 


a,  a  thermometer  c,  reading  to  0-2°,  being  arranged  with  its  bulb  exactly 
in  the  centre  of  the  liquid  mass.     The  whole  is  then  left  at  rest. 

The  temperature  is  noted  when  the  first  crystals 
appear  at  the  bottom  of  the  tube,  crystallisation  then 
occurring  at  the  surface  of  the  liquid  acids,  on  the  walls 
of  the  tube  and  in  the  mass  of  the  liquid.  When 
numerous  crystals  appear  throughout  the  liquid,  the 
mass  is  stirred  gently  with  the  thermometer  until  it 
becomes  pasty  and  opalescent  and  prevents  the  bulb 
of  the  thermometer  from  being  seen  (stirring  for  12- 
15  seconds  usually  suffices)  ;  it  is  then  left  at  rest. 

Before  and  during  the  stirring  the  column  of  the 
thermometer  is  carefully  observed.  It  falls  at  first 
slowly  and  regularly,  but  at  a  certain  point  the  fall 
slackens,  then  stops,  and  towards  the  end  of  the 
agitation  gives  way  to  a  rise  to  a  maximum,  the 
latter  persisting  for  about  two  minutes.  This  station- 
ary temperature  represents  the  solidifying  point  (titer) 
of  the  fatty  acids  examined.1 

The  result  is  controlled  by  re  melting— after  some 
time  (preferably  12  hours) — the  fatty  acids  at  a  tem- 
perature not  more  than  5°  above  the  solidifying  point 
found  and  allowing  the  molten  mass  to  solidify  in  the 
same  conditions  as  before. 

When  the  titer  of  a  tallow  is  known,  its  yields  of 
liquid  acids  (oleic)  and  solid  acids  (stearic  and  pal- 
mitic) may  be  deduced  from  Dalican's  Table  (XLVI),  which  has  been 
compiled  empirically  by  mixing  a  typical  commercial  stearine  with 
solidifying  point  54-4°  with  oleic  acid  freed  from  solid  acids  by  pro- 
longed standing  and  filtration.  It  indicates  the  percentages  of  stearic 
and  oleic  acids  in  a  tallow,  a  deduction  of  4%  having  been  made  for  the 
glycerine  and  i%  for  moisture  and  impurities. 

The  percentage  of  stearic  or  oleic  acid  in  a  mixture  of  fatty  acids  is 
given  by  the  formula 

a  x  100 

95 

where  a  is  the  percentage  of  stearic  or  oleic  acid  given  in  Dalican's  table. 

2.  Detection  of  Adulterations. —  (a)  Bone  and  wool  fats  :  by  the 
odour.  They  lower  the  saponification  number  (especially  wool  fat)  and 
if  the  unsaponifiable  matter  is  extracted,  this  contains  a  considerable  amount 
of  cholesterol  (see  General  Methods,  19). 

(b)  Palm  oil  and  coco-nut  oil ;  by  the  odour  ;  they  raise  the  saponifi- 
cation number,  and  the  latter  oil  lowers  the  iodine  number. 

1  In  place  of  the  arrangement  indicated  above,  Shukoff  uses  a  vacuum-jacketed 
vessel,  into  which  30-40  grams  of  the  fused  acid  are  poured.  The  vessel  is  then 
closed  with  a  stopper  carrying  a  thermometer,  and  when  the  first  crystals  appear  the 
apparatus  is  shaken  vigorously  up  and  down  until  the  contents  become  opaque.  It 
is  then  left  at  rest  and  the  maximum  temperature  reached  by  the  thermometer  noted . 


FIG.   58 


420 


OLEOMARGARINE 


Dalican's   Table 

TABLE    XLVI 


Solidification 

Stearic  Acid 

Oleic  Acid 

Solidification 

Stearic  Acid 

Oleic  Acid 

Point. 

O/ 
/O 

% 

Point. 

o/ 

/O 

% 

35° 

25-20 

69-80 

44-5° 

49-40 

45-60 

35'5 

26-40 

68-60 

45 

51-30 

43-70 

36 

27-30 

67-70 

45-5 

52-25 

42-75 

36-5 

28-75 

66-25 

46 

53-20 

41-80 

37 

29-80 

65-20 

46-5 

55-io 

39-90 

37'5 

30-60 

64-40 

47 

57-95 

37-05 

38 

3I-25 

63-75 

47-5 

58-90 

36-10 

38-5 

32-I5 

62-85 

48 

61-75 

33-25 

39 

33-45 

61-55 

48-5 

66-50 

28-50 

39-5 

34-20 

60-80 

49 

71-25 

23-75 

40 

35-15 

59-85 

49-5 

72-20 

22-80 

40-5 

36-10 

58-90 

50 

75-05 

I9-95 

4i 

38-00 

57-oo 

50  -5 

77-10 

17-90 

41-5 

38-95 

56-05 

5i 

79-50 

I5-50 

42 

39-90 

55-io 

5i-5 

81-90 

13-10 

42-5 

42-75 

52-25 

52 

84-00 

I  I-OO 

43 

43-70 

5i-3o 

52-5 

88-30 

6-70 

43'5 

44-65 

50-35 

53 

92-10 

2-90 

44 

47-50 

47-50 

(c)  Other  vegetable  oils  :    by  the  increase  in  the  iodine  number,  by 
colour  reactions,  and  by  testing  for  phytosterol  (see  Hog's  Fat). 

(d)  Cottonseed  stearine  :    by  Halphen's  reagent  (see  Cottonseed  Oil). 

(e)  Mineral  substances  (gypsum,  talc  and  the  like)  :    detected  in  the 
portion  insoluble  in  ether. 


Pure  tallows  of  good  quality  give  about  95%  of  fatty  acids  setting  at  about 
44°,  the  commercial  valuation  being  made  with  43-5°  as  basis  ;  the  saponifica- 
tion  number  is  195-200.  They  give  a  mean  of  about  9-5%  of  glycerine. 

According  to  the  Union  of  Italian  Soap-makers,  the  titer  of  ox- tallow  should 
not  be  below  43-5°,  while  that  of  mutton-tallow  may  vary  from  41°  to  49-8°. 
In  different  varieties  the  acidity  allowed  varies  from  3%  to  20%.  Moisture 
and  impurities  allowed  up  to  i%. 


OLEOMARGARINE 

This  is  the  semi-fluid  part  expressed  from  tallow  at  about  25°  or  even  a 
higher  temperature.  It  is  a  soft  yellowish  fat,  which  readily  decolorises 
in  the  light,  has  a  faint  odour  of  tallow  and  a  slight  agreeable  taste. 

It  gives  no  appreciable  colour  reactions  with  the  ordinary  oil  reagents, 
and  its  physical  and  chemical  characters  are  as  given  below. 

Oleomargarine  serves  as  raw  material  for  the  preparation  of  artificial 
butter  (q.v.,  Vol.  II,  Chapter  II). 


HOG'S  FAT 

The  physical  and  chemical  characters  of  oleomargarine  are  : 

Specific  gravity  at  15°  .          .          .          .          .      0-924-0-930 

„     98-100°         .....       0-859-0-863 

Melting  point    .....   32-35°  (sometimes  up  to  40°) 

,,     of  fatty  acids        ......     40-43° 

Solidifying  point  of  fatty  acids.  .....      39-42° 

Zeiss  refractometric  reading,  at  35°    .....     50-52° 

„    40°    .  .     47-49° 

Acid  number,  if  fresh  and  well  stored         .          .  .       o 

Saponification  number        .....      192-200   (195-198) 

Iodine  number.          ......  42~55  (43-48) 

Fixed  acid  number    ........       95-96 

Volatile  ,,  ,,........    0-4-1-0 

Under  the  polarising  microscope  it  behaves  like  fused  butter  (see  3  in  article 
on  Butter,  Vol.  II,  Chapter  II). 


HOG'S    FAT 

Hog's  fat  is,  strictly  speaking,  the  fat  of  the  inside  of  the  animal,  that 
adhering  to  the  inside  of  the  skin  constituting  lard. 

American  hog's  fat  is  divided  into  various  qualities  according  to  the 
method  of  preparation. 

In  general  the  fat  is  white  and  pasty,  with  a  peculiar  odour  and  a  sweetish 
taste  ;  it  becomes  rancid  easily,  turning  yellow.  It  is  only  slightly  soluble 
in  alcohol.  With  the  ordinary  reagents  for  oils  it  gives  no  colour  reactions. 
Its  characters  are  given  in  Table  XLVII. 

Detection  of  Adulterations. — Lard  is  adulterated  with  or  ^even  replaced 
by  mixtures  of  tallow,  pressed  tallow  (also  hardened  or  hydrogenised  oils), 
cottonseed  stearine  or  other  vegetable  fats,  or  cottonseed,  sesame,  arachis, 
maize,  sunflower-seed,  coco-nut  or  lard  oil ;  also  with  pressed  lard  and 
vegetable  oils.  The  artificial  mixtures  constituting  lard  substitutes  often 
contain  a  small  proportion  of  lard,  recognisable  mainly  by  its  characteristic 
odour.  Lards  containing  marked  amounts  of  water,  incorporated  with 
the  help  of  a  little  alkali,  are  also  found. 

The  various  adulterations  are  detected  as  follows  : 

1.  WATER,  ALKALI  AND  OTHER  MINERAL  SUBSTANCES.     The  water  is 
determined  by  drying  the  fat  at  100°  to  constant  weight.     Alkalis  and 
other  mineral  matters  may  be  found  by  incinerating  the  fat  and  examiring 
the  ash  ;  the  former  may  also  be  detected  by  treating  with  hot  water  and 
testing  with  litmus  paper,  or  by  passing  a  current  of  steam  for  half  an  hour 
into  a  mixture  of  60  grams  of  the  fat  with  60  grams  of  water,  then  allowing 
the  mass  to  cool  and  filtering  :  in  presence  of  an  alkali  or  an  alkaline  earth, 
a  milky  nitrate  is  obtained. 

2.  TALLOW,  PRESSED  TALLOW  OR  OTHER  ANIMAL  FAT  OR  HARDENED 
(HYDROGENISED)  OIL.     These  substances  are  tested  for  by  Bomer's  method,'1 

1  Zeitschr.  Unt.  Nahr.  Genussmittel,  1913,  XXVI,  p.  559.  See  also  papers  on  this 
method  by  Bomer,  Alpers,  Fischer  and  Werwerinke,  and  Sprinkmeyer  and  Diedrichs 
(ibid.,  1914,  XXVII,  pp.  142,  153,  361,  571). 


422  HOG'S  FAT 

based  on  the  difference  in  the  melting  points  of  (i)  the  solid  glycerides 
recrystallised  from  ether  and  (2)  the  iatty  acids  obtained  from  them. 

(a)  Preparation  of  the  glycerides.     In  a  beaker  of  about  150  c.c.  capacity, 
50  grams  of  the  fused  and  filtered  fat  are  dissolved  in  50  c.c.  of  ether,  the 
beaker  being  covered  with  a  clock-glass,  cooled  to  15°  and,  with  frequent 
shaking,  allowed  to  crystallise.     After  an  hour  the  mass  is  filtered  through 
a  funnel  containing  a  perforated  disc  covered  with  a  layer  of  filter-paper 
pulp,  the  liquid  being  pumped  off  and  the  crystalline  mass  left  in  the  funnel 
then  pressed  with  a  watch-glass  to  free  it  from  mother-liquor.     The  mass  is 
then  dissolved  again  in  50  c.c.  of  ether  and  after  an  hour  filtered  off  as  before. 

The  melting  point  of  the  glycerides  thus  obtained  is  usually  63-64° 
for  pure  lard,  but  lower  if  tallow  is  present.  If  the  melting  point  is  below 
61°,  the  glycerides  must  be  recrystallised  from  ether  in  the  manner  described 
until  a  portion  melting  at  least  as  high  as  61°  is  obtained.  To  judge  with 
certainty,  it  is  necessary  that  the  glycerides  melt  between  61°  and  65°. 

To  obtain  a  good  crystallisation  of  the  solid  glycerides  in  the  case  of 
soft  fats  rich  in  liquid  glycerides,  the  ethereal  solution  should  be  cooled 
to  5-10°,  or  use  made  either  of  a  mixture  of  3-4  parts  of  ether  with  I  part 
of  alcohol,  or  of  anhydrous  acetone. 

(b)  Preparation  oj  the  fatty  acids.     From  c-i  to  0-2  gram  of  the  glycerides, 
m.p.  61-65°,  is  finely  subdivided  and  placed  in  a  beaker  with  10  c.c.  of  about 
seminormal    colourless    alcoholic    solution    of   potassium   hydroxide.     The 
liquid  is  boiled  carefully  for  5-10  minutes  to  bring  about  saponification, 
the  soap  being  dissolved  in  100  c.c.  of  water  and  the  solution  transferred 

'to  a  separating  funnel,  decomposed  with  2-3  c.c.  of  25%  hydrochloric 
acid  and  extracted  with  25  c.c.  of  ether.  The  filtered  ethereal  solution  is 
evaporated  and  the  residue  dried  at  about  100°  for  30-60  minutes  and,  when 
cold,  finely  powdered. 

(c)  Determination   oj  the  melting  points.     The   melting   points   of   the 
glycerides  and  of  the  fatty  acids  prepared  according  to  (a)  and  (b)  are  now 
determined  under  identical  conditions.     For  this  purpose,  two  very  thin, 
perfectly  similar  U -tubes  are  used.     With  the  help  of  a  platinum  wire,  the 
finely  powdered  substance  is  introduced  into  one  of  the  limbs  of  the  U-tube 
so  as  to  form  a  layer  2-3  mm.  deep.     The  two  tubes  are  then  attached  to 
a  thermometer  so  that  the  branches  containing  the  substances  adhere  to 
the  bulb  and  the  whole  heated  in  a  water- bath  ;    when  a  temperature  of 
50°  is  reached,  the  heating  is  adjusted  so  that  the  rise  in  temperature  is 
only  1-5-2°  per  minute.     The  temperature  at  which  the  layer  becomes 
liquid,  clear  and  transparent  is  taken  as  the  melting  point.     The  deter- 
mination should  be  repeated  with  fresh  substance  and  the  mean  of  two 
concordant  results  taken. 

With  pure  hog's  fat  the  difference  (d)  between  the  melting  points  of 
the  glycerides  (M.G.)  and  of  the  fatty  acids  (M.A.),  for  values  of  M.G. 
lying  between  61°  and  65°,  is  never  less  than  the  values  in  the  following 
table  : 


HOG'S  FAT 


423 


M.G. 

d 

M.G. 

d 

M.G. 

d 

61-0° 

5-00° 

62-5° 

4-25° 

64-0° 

3-50° 

61-5 

475 

63-0 

4-00 

64-5 

3-25 

62-0 

4-50 

63-5 

375 

65-0 

3-00 

For  each  0-1°  variation  in  M.G.  the  difference  d  changes  by  0-05°,  and 
the  sum  M.G.  +  2d  is  never  less  than  71  with  pure  hog's  fat.  Hog's  fat 
containing  tallow  of  whatever  origin  or  pressed  tallow  or  hardened  oil 
gives  a  lower  value  of  d  than  is  shown  in  the  above  table,  while  M.G.  +  id, 
is  less  than  71. 

EXAMPLES  :  A  hog's  fat  gave  :  M.G.  =  63-5°  and  M.A.  =  58°,  so  that 
d  =  5-5  and  M.G.  -\-  zd  =  74-5°  ;  the  fat  is  thus  pure. 

Another  fat  gave  :  M.G.  =  63°  and  M.A.  =  60-5°,  so  that  d  =  2-5°  and 
M.G.  -(-  2d  =  68.  This  fat  contains  tallow  (pressed  tallow,  hardened  oil). 

3.  VEGETABLE  OILS  AND  FATS.  COTTONSEED  STEAKINE.  These  adul- 
terants are  detected  as  follows  : 

(a)  Colour  reactions.     Bellier's  reaction   (see  General  Methods,   23,   4) 
shows  the  presence  of  seed  oils  in  general ;  Villa vecchia  and  Fabris'  reaction 
that  of  sesame  oil  (q.v.)  ;   Halphen's  reaction  and  the  silver  nitrate  reaction 
according  to  Armani  or  Tortelli  and  Ruggeri,  that  of  cottonseed  stearine 
(see  Cottonseed  Oil). 

Arachis  oil  is  detected  by  the  reaction  for  arachidic  and  lignoceric  acids 
(see  Arachis  Oil). 

(b)  Various  characters.     Determinations  are  also  made  of  the  saponifi- 
cation,  volatile  acid  and  Polenske  numbers  (see  General  Methods,  8  and 

10  of  this  chapter,  and  Butter,  Vol.  II),  which  detect  the  presence  of  coco- 
nut oil ;  of  the  ordinary  and  absolute  iodine  numbers  (see  General  Methods, 
12  and  13),  which  serve  to  confirm  the  presence  of  seed  oils  and  to  give  an 
approximate  indication  of  their  quantity  (when  the  nature  of  the  vegetable 

011  has  been  ascertained)  ;    and  of  the  rotatory  power,  for  the  detection  of 
Hydnocarpus   (Maratti)  and  Mowrah  fats  (see  later,  d). 

As  subsidiary  determinations,  measurements  may  also  be  made  of  the 
Zeiss  refractometric  reading  at  40°  (see  Butter)  and  of  the  Maumene  number 
(see  General  Methods,  21). 

(c)  Detection  oj  phytosterol.     This  is  of  special  importance  in  the  analysis 
of  lard,  since  only  with  its  help  can  it  be  decided  if  vegetable  oils  have  really 
been  added. 

Like  all  other  animal  fats  and  oils,  hog's  fat  contains,  as  unsaponifiable 
substance,  cholesterol  (about  0-2%  in  the  crude  state),  whereas  the  un- 
saponifiable substance  of  vegetable  oils  and  fats  consists  of  phytosterol. 
The  crystalline  form  and  the  melting  point  of  the  unsaponifiable  substances 
suitably  purified  (see  General  Methods,  19)  and,  better  still,  the  melting 
point  of  their  acetyl  compounds  serve  to  detect  mixtures  of  cholesterol 
and  phytosterol. 

For  the  detection  of  phytosterol  in  lard  (and,  in  general,  in  other  animal 


424  HOG'S  FAT 

fats  and  oils),  there  are  two  suitable  methods,  the  second  being  the  more 
convenient. 

(1)  The  alcohol  method,  according  to  Forster  and  Riechelmann x  :  50 
grams  of  the  fat  and  75  c.c.  of  95%  alcohol  are  boiled  for  5-10  minutes  in 
a  flask  fitted  with  a  reflux  condenser,  the  alcoholic  liquid  being  separated 
while  still  hot  and  the  boiling  repeated  with  a  further  75  c.c.  of  alcohol. 
The  united  alcoholic  liquids,  which  contain  the  unsaponifiable  substances, 
are  boiled  with  15  c.c.  of  30%  sodium  hydroxide  solution  until  saponifica- 
t  ion  is  complete,  the  liquid  being  evaporated  almost  to    dryness    and   the 
residue  extracted  with  ether.     The  ethereal  solution  is  evaporated  to  dry- 
ness  and  the  residue  left  taken  up  in  a  little  ether,  filtered  and  again 
evaporated.     The  final  residue  is  dissolved  in  a  little  boiling  95%  alcohol 
containing  a  few  drops  of  dilute  acetic  acid  and  crystallised. 

Repetition  of  the  crystallisation  from  a  little  boiling  absolute  alcohol 
yields  the  sterols  (cholesterol  and  phytosterol)  ready  for  microscopic  exami- 
nation. With  practice  and  by  comparisons  of  mixtures  of  known  com- 
position, the  crystalline  form  observed  under  the  microscope  indicates  if 
the  cholesterol  is  pure  or  mixed  with  phytosterol ;  the  characteristic  form 
of  the  latter  is  evident  in  mixtures  containing  only  5%  of  vegetable  oil  (see 
figures  given  under  General  Methods,  19). 

The  acetyl  compound  is  then  prepared  as  follows  :  All  the  crystals, 
together  with  the  last  mother-liquor,  are  freed  from  alcohol  by  heating  in 
a  glass  dish  on  a  water-bath,  the  residue  being  boiled  for  a  moment  with 
3-5  c.c.  of  acetic  anhydride,  the  dish  being  covered  with  a  clock-glass  mean- 
while ;  the  cover  is  then  removed  and  the  solution  evaporated  to  dryness 
on  a  water- bath.  The  residue  is  dissolved  in  boiling  absolute  alcohol  (about 
20  c.c.)  and  the  solution  left  to  crystallise  at  the  ordinary  temperature. 
When  about  two-thirds  of  the  alcohol  have  evaporated,  the  crystals  are 
collected  in  a  small  filter  and  washed  with  2-3  c.c.  of  95%  alcohol,  the  filter 
being  then  dried  by  pressing  between  filter-paper  and  the  crystals  redis- 
solved  in  5-10  c.c.  of  boiling  absolute  alcohol  and  left  to  crystallise.  This 
operation  is  repeated  three  times.  After  the  third  crystallisation,  the 
melting  point  of  the  crystals  is  determined,  two  further  crystallisations 
followed  by  determinations  of  the  melting  point  being  carried  out  (see  later). 

(2)  Digitonin  method 2 :    50   grams   of   the   fat  are  dissolved  in  about 
120  c.c.  of  chloroform  and  the  liquid  heated  on  the  water-bath  at  about 
60°  with  20  c.c.  of  a  i%  solution  of  digitonin  in  96%  alcohol,  with  frequent 
shaking  ;  it  is  then  left  at  rest  overnight.     The  cholesterol  and  phytosterol 
combine  with  the  digitonin  forming  insoluble  products  (digitonides),  which 
are  deposited  at  the  bottom  of  the  chloroform  solution  of  the  fat.     The 
liquid  is  filtered  and  the  precipitate  washed  on  the  filter  with  chloroform 
and  dried  in  the  air. 

1  Zeitschr.  fur  offentl.  Chem.,  1897,  p.  10. 

2  This  method  may  be  applied  under  the  conditions  laid  down  by  Marcusson  and 
Schilling  (Chem.  Zeit.,  1913,  p.  1001)  or  by  Klostermann,  Fritzsche,  or  Klostermann 
and  Opitz  (Zeitschr.    Unt.  Nahr.  Genussmittel,   1913,   XXVI,  pp.  433,   614,  and  1914, 
XXVII,  p.  713).     The  method  now  described  is  deduced  from  these,  with  modifications 
found  valuable  as  a  result  of  tests  made  in  the  Italian  Central  Customs  Laboratory  by 
Dr.  L.  Settimj. 


HOG'S  FAT  425 

The  digitonides  thus  obtained  are  boiled  for  15-20  minutes,  in  a  flask 
fitted  with  a  reflux  condenser,  with  about  20  c.c.  of  acetic  anhydride,  the 
liquid  being  then  evaporated  to  dryness  in  a  glass  dish  on  the  water-bath, 
the  mass  being  stirred  towards  the  end  with  a  glass  rod.  The  residue  is 
recrystallised  several  times  from  95-96%  alcohol  and  the  melting-point  of 
the  acetyl-compound  thus  obtained  determined  after  the  second,  third  or 
fourth  crystallisation. 

Melting  point  oj  the  acetyl-compound.  This  is  determined  in  a  very 
thin  glass  U-tube,  into  one  branch  of  which  the  powdered  substance  is 
introduced  to  form  a  layer  2-3  mm.  deep.  The  observed  melting  point 
is  then  corrected  by  means  of  the  formula, 

x  =  T  +  [n(  T—t)  X  0-000154], 

where  x  =  correct  melting  point, 

T  =  observed  melting  point, 

n  —  length  of  meicury  column  of  thermometer  protruding  from  the 
bath,  expressed  in  degrees,1 

t  =  mean  temperature  of  the  air  about  the  protruding  part  of  the 
thermometer,  determined  with  another  thermometer  placed  near  the  first 
and  with  its  bulb  at  the  middle  of  the  protruding  portion  of  the  stem.2 

The  corrected  melting  point  of  cholesterol  acetate  is  H4-3-ii4-8°,  whilst 
that  of  phytosterol  acetate  is  above  125°. 

(d)  Rotatory  power.  This  is  determined  on  the  fat  as  such  or  on  the 
unsaponifiable  substances  extracted  from  it.  In  the  former  case,  which 
serves  for  the  detection  of  Hydnocarpus  oil,  the  rotatory  power  of  the  fat 
is  determined  in  benzene  solution  at  a  temperature  of  about  20°  with  an 
ordinary  shadow  polarimeter.  From  the  observed  rotation  the  specific 
rotation  [a]|°  is  calculated  by  means  of  the  formula, 


where  a  is  the  observed  angle  in  circular  degrees,  /  the  length  in  decimetres 
of  the  tube  used,  and  c  the  concentration,  i.e.,  the  number  of  grams  of  sub- 
stance in  100  c.c.  of  the  solution. 

The  determination  of  the  rotatory  power  of  the  unsaponifiable  substance 
is  effected  in  the  manner  indicated  by  Berg  and  Angerhausen  for  the  detec- 
tion of  Mowrah  butter  in  lard.3 


Genuine  hog's  fat  should  not  contain  appreciable  quantities  of  water,  alkaline 
substances  or  other  mineral  matters,  and  should  be  free  from  all  extraneous 
fats  and  oils. 

Its  physical  and  chemical  characters  should  lie  within  the  limits  given  in 
Table  XLVII.  A  saponification  number  above  200,  volatile  acid  and  Polenske 
numbers  higher  than  i,  and  an  iodine  number  below  45  demonstrate  the  presence 

1  For  instance,  if  the  thermometer  is  immersed  up  to  -f-  5°  and  the  observed  melting 
point  is  1  15,  n  =  115  —  5. 

2  For  melting  points  between  100°  and  150°,  t  =  50-56°. 

3  Zeitschr.  Unt.  Nahr.  Genussmittel,  1914,  XX  VII,  p.  723. 


426  BONE  FAT 

of  coco-nut  oil.  Ordinary  and  absolute  iodine  numbers  exceeding  the  limiting 
values  yet  observed  show  the  presence  of  vegetable  oils. 

Its  specific  rotation  should  be  very  low  and  negative  (about  — 0-06°)  ;  if 
it  is  positive,  the  presence  of  Hydnocarpus  oil  (poisonous),  which  has  the  specific 
rotation  about  55°,  is  assumed. 

It  should  not  contain  arachidic  and  lignoceric  acids. 

It  should  not  give  any  colour  reaction  for  seed  oils.  It  must,  however,  be 
borne  in  mind  that  a  slight  coloration  may  be  given  by  lard  from  hogs  fed  with 
cottonseed,  sesame  or  other  seed  cake.  In  such  cases,  addition  of  seed  oil  to 
the  lard  is  proved  only  when  the  presence  of  phytosterol  is  certain.  This  is 
the  case  when  the  acetyl-compound  of  the  sterols  obtained  as  described  above 
has  a  corrected  melting  point  higher  than  115°. 

Lard  which  gives  the  colour  reactions  but  does  not  contain  phytosterol 
cannot  be  regarded  as  containing  vegetable  oil. 

The  melting  point  difference,  determined  by  Bomer's  method,  should  be 
such  that  the  value  of  M.G.  -|-  2d  is  71  or  more  ;  if  this  value  is  less  than  71, 
the  lard  is  considered  adulterated  with  tallow,  pressed  tallow  or  hardened  oil. 

In  general,  the  following  conclusions,  based  on  the  melting  point  difference 
and  the  phytosterol  test,  may  be  drawn  * : 

I.  The  melting  point  difference  is  normal  :    the  lard  is  either  pure  or  adul- 
terated with  vegetable  oils.     The  phytosterol  test   (m.pt.   of  the  acetyl-com- 
pound of  the  sterols)  will  demonstrate  the  presence  or  absence  of  vegetable  oil. 

II.  The  melting  point  difference  is  below  the  normal  (M.G.  -j-  2d  less  than 
71)  :    the  following  cases  present  themselves  : — 

1.  Phytosterol  test  negative  :    lard  contains  tallow,  hardened  animal  oils 
or  both. 

2.  Phytosterol  test  positive  :    there  may  be — 
(a)  Addition  of  vegetable  oils  or  hardened  oils  ; 

(6)         ,,          of  tallow  (or  pressed  tallow)  and  vegetable  oils  or  fats  ; 
(c)         ,,  ,,  ,,  ,,  ,,    hardened  vegetable  oils. 


BONE    FAT 

This  is  obtained  by  de-fatting  bones  by  means  of  water,  steam  or  solvent 
(benzine,  carbon  disulphide).  It  varies  in  consistency  but  is  usually  soft 
and  granular,  and  it  has  a  yellowish  or  brown  colour  and  a  repulsive  odour. 
It  is  somewhat  soluble  in  alcohol,  especially  when  it  contains  much  free 
acid.  The  physical  and  chemical  characters  vary  somewhat  according  as 
the  fat  is  pure  or  has  been  extracted  with  solvents  or  steam  ;  they  are  given 
in  Table  XL VI  I. 

Bone  fat  contains  cholesterol  and,  in  accordance  with  the  method  of 
extraction,  it  may  contain  various  impurities,  such  as  water,  lime  soaps, 
gelatinous  substances  and  hydrocarbons. 

The  analysis  of  bone  fat  for  the  purpose  of  determining  its  commercial 
value,  includes  the  following  : 

1 .  Determination  of  the  Water. — As  indicated  in  the  general  methods, 
or  more  accurately  by  heating  about  10  grams  of  the  fat  at  120°  in  a  current 
of  hydrogen  to  constant  weight. 

2.  Determination  of  Extraneous  Impurities   (soaps,  mucilaginous 
and  gelatinous  substances,  etc.). — 50  grams  of  the  fat  are  well  shaken 
with  a  quantity  of  ether  sufficient  to  dissolve  the  fatty  matter  in  the  cold, 

1  Bomer  :    Zeitschr.  Nahr.  Genussmittel,  1914,  XXVII,  p.  158. 


BONE  FAT  427 

and  left  for  some  hours.  The  insoluble  matter  is  collected  on  a  weighed 
filter  and  washed  with  ether  until  the  latter  dissolves  nothing  further,  the 
filter  being  then  placed  on  a  clock-glass,  dried  at  100°  and  weighed.  The 
total  impurity  (gelatine,  lime  soaps,  etc.)  in  the  fat  is  thus  determined. 

If  account  is  to  be  taken  also  of  the  fat  combined  as  lime  soap,  treatment 
of  the  substance  with  ether  is  preceded  by  an  hour's  heating,  with  occasional 
shaking,  on  the  water- bath  with  3-5  drops  of  concentrated  hydrochloric 
acid  ;  the  lime  soaps  having  been  decomposed  in  this  way,  the  further 
procedure  is  as  described  above. 

3.  Determination   of  the   Ash. — 10  grams  of  the  fat  are   carefully 
incinerated  and  the  residue  weighed.     The  ash  of  bone  fat  is  composed  of 
calcium  oxide  and  a  little  carbonate,  with  small  quantities  of  calcium  phos- 
phate, alumina  and  ferric  oxide. 

4.  Titer.— As  with  tallow,  the  titer  of  bone  fat  is  given  by  the  solidifying 
point  of  the  free  fatty  acids,  this  being  determined  as  in  the  case  of  tallow 
(q.v.). 

5.  Acid   and   Saponification    Numbers. — By  the  general  methods, 
7  and  8.     The  acidity  is  expressed  as  percentage  of  oleic  acid. 

6.  Hydroxy -acids. — As  in  General  Methods,  15. 

7.  Unsaponifiable  Substances.- — -These  may  be  estimated  by  saponi- 
fying the  fat  with  alcoholic  potash  and  extracting  the  aqueous  solution  of 
the  soap  with  ether  (see  General  Methods,  19). 

8.  Recognition  of  Bone  Fat  which  has  been  extracted  with  Ben- 
zine.— According  to  Gianoli,1  this  may  be  effected  as  follows  : 

(a]  The  fat   is  subjected  to  prolonged  distillation  with  concentrated 
calcium  chloride  solution  ;   where  the  fat  has  been  extracted  with  benzine, 
oily  drops  which  are  not  soluble  in  soda  float  on  the  surface  of  the  distillate. 

(b)  The  fat  is  saponified  with  alcoholic  sodium  hydroxide,  the  alcohol 
expelled,  the  fatty  acids  liberated  and  washed  with  water,  and  this  water 
treated  in  the  hot  with  ammonia  :    turbidity  indicates  the  use  of  benzine. 

9.  Test  for  American  Bone  Fat.2 — To  ascertain  if  a  sample  of  bone 
fat  of  American  origin  may  be  used  without  inconvenience  for  soap-making, 
the  following  test  is  recommended  : 

100  grams  of  the  fat  and  30  c.c.  of  water  are  well  shaken  in  a 
small  steam- heated  vessel  with  20  grams  of  sulphuric  acid  (66°  Baume), 
the  mass  being  afterwards  heated  and  then  left  to  stand  :  if  the  fat  separates 
sharply  and  rapidly,  it  may  be  regarded  as  of  good  quality,  but  if  an  emulsion 
difficult  to  separate  forms,  the  fat  will  give  poor  results  and  a  bad  yield  of 
glycerine. 


* 
*  * 


Commercial  bone  fats  may  have  somewhat  varying  characters  and  com- 
position :  the  water  content  usually  ranges  from  i  to  3%,  but  may  reach  even 
20%  ;  extraneous  impurities  vary  from  0-5  to  3%  and  the  ash  also  from  0-5 
to  3%.  The  titer  for  good  products  is  36-44°,  the  acidity  may  exceed  50%, 
and  the  unsaponifiable  matters  usually  lie  between  0-5  and  2%. 

The  permissible  limits  for  good  bone  fats  for  soap-making  are  :  impurities, 
up  to  3%  (lime  and  magnesia  soaps,  iron,  moisture,  mucilaginous  matter,  higher 

1  Ind.  Sapon.,  1909,  p.  3.  2  Ind.  Sapon.,  1914,  p.  102. 


428  FOOT  OIL 

alcohols,  hydrocarbons,  etc.)  ;    hydroxy-acids,  up  to  2%  ;    acidity,  not  above 
50%  ;    saponification  number,   185-195  ;    titer,  36-42°. 


FOOT    OIL 

This  is  obtained  more  especially  from  the  feet  of  the  ox,  but  also  from 
those  of  the  sheep  and  horse.  It  is  a  pale  yellow,  almost  odourless  liquid, 
solidifying  only  below  o°  (at  about  —5°).  Its  characters  are  indicated  in 
Table  XLVII. 

Detection  of  Adulterations. — The  oil  may  be  adulterated  with  mineral, 
vegetable  or  marine  animal  oils,  these  additions  being  detectable  by  deter- 
mining the  various  characters  of  the  oil.  Mineral  oils  lower  the  specific 
gravity  and  the  saponification  and  iodine  numbers  and  may  be  identified 
by  investigation  of  the  unsaponifiable  substances  (see  General  Methods,  19). 
Vegetable  oils  give  Bellier's  reaction  and  the  other  general  reactions  of 
seed  oils  (see  General  Methods,  23).  By  means  of  the  special  reactions  and 
tests,  colza,  cottonseed  and  sesame  oils  (q.v.)  may  be  identified.  Pure 
foot  oil  gives  no  colour  reaction  and  does  not  contain  arachidic  and  lignoceric 
acids  or  erucic  acid.  The  presence  of  phytosterol  would  serve  to  confirm 
adulteration  with  vegetable  seed  oil  (see  Hog's  Fat).  Marine  animal  oils 
raise  the  specific  gravity  and  the  iodine  number  and  may  be  identified  by 
the  special  reactions  indicated  in  the  article  on  fish  oils,  etc. 


For  use  as  lubricants,  foot  oil  should  remain  liquid  and  clear  at  o°  for  a 
long  time,  should  not  contain  more  than  2%  of  free  acids  calculated  as  oleic 
acid,  and  should  not  contain  extraneous  oils.  A  drop  lying  in  a  thin  film  on 
a  glass  plate  and  kept  at  50°  for  24  hours  should  not  resinify  or  dry  up  but 
should  be  easily  removable  from  the  glass. 


Fish  and  other  Marine  Animal  Oils 

These  oils  may  be  divided  into  three  classes  :  (i)  Fish  oils  proper, 
obtained  from  herrings,  sardines,  pilchards,  sprats,  tunny  fish,  shad,  or 
from  the  residues  obtained  in  the  preparation  of  these  fish  ;  (2)  Blubber 
oils  (train  oils),  from  the  marine  mammifers,  the  seal  and  whale  ;  and  (3) 
Liver  oils,  mainly  from  cod-liver  but  to  a  small  extent  from  the  liver  of  the 
ray,  skate,  etc. 

Fish  and  blubber  oils  and  cod-liver  oil  are  treated  separately  in  the  two 
following  articles  ;  here,  however,  we  shall  give  certain  special  reactions 
which  are  common  to  the  three  classes  of  oil  and  serve  to  distinguish  all  these 
oils  from  other  fatty  substances,  either  animal  or  vegetable. 

Characteristic  Reactions. — These  reactions,  which  are  now  known 
to  be  trustworthy,  are  the  following  : 

(a)  REACTION  OF  THE  OCTABROMO-COMPOUNDS  (given  by  Halphen,  and 
modified  by  Lewkowitsch,  Marcusson  and  Huber)  :  From  about  20  c.c. 
of  the  oil  the  fatty  acids  are  extracted  in  the  usual  manner,  10  c.c.  of  the 
acids  being  then  shaken  vigorously,  in  a  cylinder  with  a  ground  stopper, 


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430  FISH  AND  BLUBBER  OILS 

with  200  c.c.  of  Halphen's  reagent  (28  vols.  of  glacial  acetic  acid,  4  vols. 
of  nitrobenzene  and  i  vol.  of  bromine)  :  a  yellow  precipitate  of  bromo- 
compounds  is  obtained.  After  an  hour's  rest,  the  liquid  is  filtered  off  by 
means  of  a  pump  and  the  precipitate  washed  with  cold  ether,  powdered 
and  boiled  for  half  an  hour  in  a  reflux  apparatus  with  benzene  (50  c.c.  of 
benzene  per  gram  of  precipitate)  :  the  o'ctabromo-compounds  of  the  fatty 
acids  of  marine  animal  oils  remain  undissolved  by  boiling  benzene.  The 
liquid  is  filtered  through  a  steam-heated  filter  and  the  precipitate  insoluble 
in  benzene  washed  with  boiling  benzene,  dried,  and  a  determination  made 
of  its  melting  point,  which  should  be  above  190°  (with  incipient  decom- 
position and  blackening).  If  the  melting  point  is  below  190°,  the  precipitate 
is  taken  up  several  times  with  boiling  benzene  until  a  portion  boiling  above 
this  temperature  is  obtained. 

A  reaction  similar  to  the  above  is  given  also  by  the  drying  oils — linseed, 
walnut  and  hempseed  oils  (see  Linseed  Oil)  ;  the  hexabromo-compounds  fur- 
nished by  these  oils  are,  however,  soluble  in  boiling  benzene  and  melt  at  175- 
180°  without  decomposing. 

According  to  Marcusson,  the  octabromo-compound  test — which  is  often 
made  on  the  fatty  acids  and  not  on  the  oil  as  such — is  able  to  detect  10  %  of 
marine  animal  oil  mixed  with  linseed  or  other  oil. 

(b)  TORTELLI  AND  JAFFE'S  REACTION.  In  a  graduated  glass  cylinder 
with  a  ground  stopper,  i  c.c.  of  the  oil,  6  c.c.  of  chloroform  and  i  c.c.  of 
glacial  acetic  acid  are  shaken  together  and  40  drops  of  a  10%  solution  of 
bromine  in  chloroform  added  ;  the  cylinder  is  again  shaken  vigorously  for 
a  moment  and  then  placed  on  a  white  paper  and  the  colour  of  the  liquid 
observed.  Marine  animal  oils  in  general  give  a  green  coloration  with  a 
yellowish  or  blue  reflexion,  which  increases  during  the  space  of  half  an  hour 
and  afterwards  changes  to  brown.  With  vegetable  or  terrestrial  animal 
oils  and  fats,  pale  yellow  or  yellowish  colorations  are  obtained,  these  grad- 
ually darkening  for  an  hour  and  then  changing  to  brown. 

For  the  reaction  to  succeed,  the  oil  and  the  reagents  must  be  perfectly 
dehydrated  and  the  vessels  very  dry.  If  the  oil  is  highly  coloured,  it  may 
be  decolorised  with  sulphuric  acid  x  or  soda.2 

FISH    AND    BLUBBER    OILS 

Fish  oils  proper  are  those  obtained  from  the  residues  left  during  the 
preparation  of  various  fish  (sardines,  herrings,  shad,  tunnyfish,  etc.).  From 
cetaceans  are  obtained  mainly  Whale  oil  and  Seal  oil,  dolphin  oil  and  por- 
poise oil  being  less  common.  In  general  these  oils  are  liquid  and  often 
they  are  turbid  and  contain  more  or  less  abundant  solid  deposits ;  they 

1  50    c.c.    of   the  oil  are   treated  for  5-6  hours,  with   occasional  shaking,  with  0-5 
gram  of  cone,  sulphuric  acid  and  then  filtered  through  a  thin  layer  of  fuller's  earth  : 
the  filtrate  is  washed  with  boiling  water  to  render  it  free  from  acid  and  filtered  through 
paper  in  an  oven  at  100°. 

2  100  c.c.  of  the  oil  and  5  c.c.  of  30%  caustic  soda  solution  are  heated  on  the  water- 
bath  for  a  quarter  of  an  hour  with  frequent  shaking,  50-60  c.c.  of  saturated  sodium 
chloride  solution  being  then  added  and  the  heating  on  the  water-bath  continued  for 
three-quarters  of  an  hour,  with  shaking.     The  oil  is  then  decanted  off,  washed  two 
or  three  times  with  hot  water  and  filtered  in  an  oven  at   100°. 


COD-LIVER   OIL  431 

are  coloured  pale  yellow  to  brownish  red  and  have  a  more  or  less  unpleasant 
odour.  With  alcoholic  potash  they  mostly  give  brown  soaps  ;  they  contain 
small  quantities  of  unsaponifiable  substances  (0-5-2%).  When  dissolved 
in  carbon  disulphide  and  treated  with  a  little  cone,  sulphuric  acid,  they 
give  a  reddish-brown  coloration  with  no  trace  of  violet  (see  Cod-liver  Oil). 
They  give  the  general  reactions  for  marine  animal  oils  described  above 
and  their  characters  are  given  later  in  Table  XL VII  I. 
Their  analysis  includes  the  following  : 

1.  Water,  Impurities,  Acidity. — These  are  determined  as  in  General 
Methods,  i  and  7. 

2.  Distinction  between  Fish  Oils  and  Blubber  Oils. — With  pure 
oil  of  one  kind  or  the  other,  the  iodine  and  Maumene  numbers  are  sufficient 
to  determine  if  it  is  fish  oil  or  whale  (or  seal)  oil  (see  Table  XLVIII).     Mix- 
tures of  the  two  types  of  oil  cannot  be  identified. 

The  reaction  with  carbon  disulphide  and  sulphuric  acid  serves  to  dis- 
tinguish fish  and  blubber  oils  from  liver-oils  (see  following  article). 

3.  Detection  of  Impurities  : 

(a)  MINERAL  AND  RESIN  OILS.    These  are  detected  by  saponifying  the 
oil  (50-100  c.c.)  and  extracting  and  examining  the  unsaponifiable  matter 
as  indicated  in  General  Methods,  19. 

(b)  VEGETABLE  OILS.     These  are  detected  by  the  digitonin  test  for 
phytosterol  (see  Hog's  Fat).     Cottonseed  and  sesame  oil  may  also  be  iden- 
tified by  means  of  their  special  colour  reactions,  provided  that  the  oil  is  not 
too  much  coloured. 


COD-LIVER    OIL 

This  is  obtained  from  the  liver  of  Gadus  morrhtta  and  of  other  allied  fish 
of  the  Northern  Atlantic.  According  to  its  purity  and  colour  it  is  divided 
into  :  white  (medicinal,  superior),  which  is  clear,  of  pale  or  straw  yellow 
colour,  almost  odourless  and  almost  tasteless  ;  pale,  which  is  clear,  reddish- 
yellow,  and  with  a  marked  fishy  odour  and  taste  ;  red  or  brown,  which  is  more 
or  less  turbid  and  brownish-red  and  with  an  unpleasant  fishy  odour  and 
taste. 

It  dissolves  slightly  in  alcohol,  but  easily  in  ether,  benzene  or  other 
ordinary  fat  solvent.  It  contains  small  quantities  of  unsaponifiable  sub- 
stances (mainly  cholesterol)  :  0-3-2%  in  pale  oils  and  up  to  about  8%  in 
crude  brown  ones. 

Further  it  contains  traces  of  iodine  in  organic  combination  (0-0002- 
0-04%).  This  is  not  extractable  by  solvents  or  by  mere  saponification,  but 
is  detected  only  by  saponifying  the  oil,  adding  a  little  nitre  to  the  soap, 
evaporating  to  dryness,  incinerating  and  carefully  calcining  and  testing 
the  ash  for  iodine  in  the  usual  way. 

It  gives  the  general  reactions  of  marine  animal  oils  described  above, 
and  its  characters  and  those  of  the  livers  of  other  fish  are  given  in  Table 
XLVIII.  The  determinations  to  be  made  are  : 

1.  The  Special  Reaction  for  this  oil,  but  common  to  all  others  from 
fish-livers,  is  as  follows  :  A  drop  of  the  oil  is  dissolved  in  2  c.c.  of  carbon 


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432 


WAXES 


433 


disulphide  and  the  solution  gently  shaken  with  a  small  drop  of  cone,  sul- 
phuric acid  :  a  fine  purple-violet  coloration,  rapidly  changing  to  brownish- 
red,  is  obtained. 

Other  marine  animal  oils,  treated  similarly,  give  no  violet  coloration 
(see  preceding  article). 

2.  Acid  Number. — -As  in  General  Methods,  7. 

3.  Test  for  Added  Iodine   (Inorganic)  .—About   10  c.c.  of  oil  are 
shaken  with  as  much  water,  the  latter  being  then  separated  and  treated 
with  starch  paste  and  either  cone,  nitric  acid  or  chlorine  water :    appear- 
ance of  a  blue  coloration  indicates  inorganic  iodine. 

4.  Freezing   Point. — The  oil  is  maintained  at  o°  for  some  time  to 
ascertain  if  it  remains  liquid. 

5.  Detection  of  Adulterations  .—The  oil  may  contain  the  following 
admixtures  : 

(a)  OTHER  FISH-LIVER  OILS.     No  certain  methods  are  known  of  dis- 
tinguishing different  fish-liver  oils  or  their  mixtures.  . 

i  (b)  FISH  AND  BLUBBER  OILS.  No  certain  method  exists  of  detecting 
fish-oil  in  cod-liver  oil.  Addition  of  blubber  oil  (whale,  seal)  may  be  sus- 
pected as  a  result  of  determinations  of  the  iodine  number,  the  Maumene 
number  and  the  refractometer  reading  (Zeiss),  which  are  lowered  by  whale 
or  seal  oil  (see  Table  XLVIII). 

(c)  VEGETABLE   AND    MINERAL    OILS.     These   are    recognised   by   the 
methods  given  in  the  preceding  article  (Fish  and  Blubber  Oils). 


* 
*  * 


According  to  the  Official  Italian  Pharmacopoeia,  medicinal  cod-liver  oil  is 
amber  or  straw- yellow,  D  at  15°  =  0-922-0-930,  iodine  number  =  150-170. 
When  cooled  to  o°  it  does  not  congeal,  but  deposits  flocks  of  white  solid  matter. 
It  should  give  the  reaction  for  fish-liver  oils  and  should  contain  no  inorganic 
iodine  (test  3). 

The  acidity  is  low  in  white  oils,  especially  in  so-called  steam  liver  oil  (0-3- 
2%  as  oleic  acid),  but  is  higher  (up  to  8%)  in  the  more  highly  coloured  yellow 
or  pale  oil  and  may  reach  about  30%  in  brown  oils. 


Waxes 

Waxes  are  composed  essentially  of  compounds  of  certain  fatty  acids 
(palmitic,  stearic,  cerotic)  with  higher  alcohols  (cetyl,  myricyl  alcohols)  ; 
some  contain  also  a  certain  amount  of  free  acids  (beeswax,  carnauba  wax) 
and  solid  hydrocarbons  (beeswax).  Waxes  are  of  animal  origin,  such  as 
beeswax,  Chinese  insect  wax,  wool  fat  and  spermaceti,  and  of  vegetable 
origin,  such  as  carnauba  wax,  fig  wax,  ocuba  wax,  etc.  The  latter  should 
not  be  confused  with  other  vegetable  products  known  as  waxes,  these  being 
really  fats,  such  as  Japan  wax  and  myrtle  wax  (see  Vegetable  Fats). 

The  waxes  of  greatest  importance  are  :  beeswax,  wool  fat,  spermaceti 
and  the  corresponding  oil,  which  are  dealt  with  in  detail.  Of  the  other 
waxes  the  characters  are  given  in  Table  XLIX. 

A.C.  28 


434  BEESWAX 

BEESWAX 

Crude  (virgin)  wax  in  pale  yellow  or  brown.  European  qualities  are 
yellow  or  pale  yellow,  the  African  and  American  reddish- yellow  to  brown, 
and  the  Indian  greyish- brown.  It  is  fatty  to  the  touch  and  soft  and  plastic 
to  the  heat  of  the  hand,  and  presents  a  granular  fracture.  It  has  a  special 
odour,  recalling  that  of  honey,  and  a  faintly  balsamic  taste. 

White  or  bleached  wax  (decolorised  by  air  and  light  or  by  chemical  means) 
is  white,  brittle,  and  only  slightly  fatty  and  odoriferous. 

In  general  the  wax  is  almost  insoluble  in  cold  alcohol  but  partly  soluble 
in  boiling  absolute  alcohol,  from  which  it  separates  on  cooling.  It  is  slightly 
soluble  in  cold  ether,  more  so  in  boiling  ether,  chloroform  or  benzene. 

It  consists  principally  of  cerotic  acid  and  myricyl  palmitate  (myricin), 
but  contains  also  free  melissic  acid  and  ceryl  alcohol  and  hydrocarbons 
(3-12%,  according  to  the  origin). 

The  physical  and  chemical  characters  of  different  types  of  beeswax  are 
given  in  Table  XLIX. 

The  wax  may  be  adulterated  with  stearine,  colophony,  paraffin  wax 
or  ceresine,  Chinese  (insect)  wax,  carnauba  wax,  Japan  wax  (so-called), 
tallow,  wool  fat,  flour  or  starch,  and  mineral  substances  ;  water  may  also 
be  present.  The  colour  may  be  enhanced  by  turmeric  or  coal-tar  colours. 

Imitations  of  the  wax  are  made  with  paraffin  wax,  ceresine  and  colophony, 
or  with  various  mixtures  of  paraffin  wax,  carnauba  wax,  Japan  wax,  stearine, 
etc.,  often  coloured  with  coal-tar  colours. 

To  detect  the  different  adulterations  and  imitations  here  indicated,  it 
is  necessary  to  determine  the  various  characters  (see  1-5)  and  further  to 
apply  certain  special  tests  (see  6-13),  since  it  is  possible  to  prepare  mixtures 
with  the  characters  of  the  pure  wax.  If,  on  the  other  hand,  the  detection 
of  beeswax  in  mixtures  with  other  substances  is  required,  test  14 is  employed. 

In  the  case  of  the  crude  (virgin)  wax,  before  proceeding  to  the  analysis 
(with  the  exception  of  the  determinations  12),  it  is  well  to  boil  the  sample 
with  water  to  remove  the  whole  of  the  honey  and  then  to  filter  the  fused 
mass  in  the  hot. 

1.  Specific  Gravity. — This  may  be  determined  most  exactly  by  means 
of  the  specific  gravity  bottle,  but  Hager's  method  may  also  be  used.     The 
wax  is  melted  at  a  gentle  heat  and  poured  in  drops  into  cold  70%  alcohol, 
the  beads  of  wax  thus  obtained  being  dried  in  absorbent  paper,  left  over- 
night to  solidify  and  then  immersed  in  alcohol  of  known  specific  gravity, 
e.g.,  0-965,  at  15°.     If  the  beads  remain  suspended  at  any  point  of  the 
liquid,  the  specific  gravity  of  the  wax  is  that  of  the  liquid,  i.e.,  0-965  ;   if, 
on  the  other  hand,  they  sink  or  float,  tests  are  made  with  more  dilute  or 
more  concentrated  alcohols  until  the  correct  specific  gravity  is  obtained. 
It  is  usually  sufficient  to  prepare  eight  or  ten  alcohol  solutions  with  specific 
gravities  from  0-960  upwards. 

It  is  also  desirable  to  determine  the  specific  gravity  of  the  wax  at  98-100° 
(see  General  Methods,  3). 

2.  Melting  Point. — As  in  General  Methods,  4. 

3.  Acid  and  Saponification  Numbers. — These  may  be  determined 


BEESWAX  435 

as  in  General  Methods  (7  and  8),  the  titration  of  the  free  acids  being  made 
on  the  hot  (almost  boiling)  alcoholic  solution  of  the  substance  with  a 
standard  alcoholic  potassium  hydroxide  solution  (about  seminormal),  while 
for  the  determination  of  the  saponification  number  the  substance  is  boiled 
with  the  alcoholic  solution  for  at  least  two  hours  on  an  asbestos  card  over 
the  naked  flame,  the  wax  being  difficultly  saponifiable. 

More  exact  determinations  may  be  made  by  Berg's  method,  modified 
by  Bohrisch  and  Kurschnei  :  about  4  grams  of  the  wax,  20  c.c.  of  xylene 
(recently  distilled)  and  20  c.c.  of  absolute  alcohol  (neutralised)  are  boiled 
in  a  reflux  apparatus  for  5-10  minutes  ;  titration  of  the  liquid  with  semi- 
normal  alcoholic  potash  (with  phenolphthalein)  gives  the  acid  number. 
A  further  quantity  of  30  c.c.  of  the  same  potash  solution  is  then  added, 
the  liquid  boiled  for  an  hour,  treated  with  50-75  c.c.  of  96%  alcohol  (neu- 
tralised), heated  for  5  minutes  longer,  and  the  excess  of  potash  titrated 
with  seminormal  hydrochloric  acid  (indicator  as  above)  ;  the  ester  number 
is  thus  obtained. 

In  judging  a  wax  (see  later)  it  is  important  to  know  the  acid,  saponification 
and  ester  numbers,  the  last  being  the  difference  between  the  first  two. 

The  ratio  of  ester  number  to  acid  number,  the  so  called  ratio  value,  is  also 
of  importance. 

4.  Iodine  Number. — As  in  General  Methods,  12. 

5.  Refractometric    Reading. — This    is    determined    with    the    Zeiss 
butyro-refractometer  (see  Butter,  Vol.  II,  Chapter  II)  at  a  temperature  of 
64°.     To  reduce  the  reading  to  the  normal  temperature  of  40°,  the  difference 
between  64  and  40,  i.e.,  24,  is  multiplied  by  0-53  and  the  product  added  to 
the  reading  at  64°. 

6.  Test  for  Stearine. — About  3  grams  of  the  wax  and  10  c.c.  of  85% 
alcohol  are  heated  and  shaken  in  a  flask  until  the  wax  is  thoroughly  fused 
and  then  left  to  cool  for  some  hours  with  frequent  shaking  ;  only  the  stearine 
(and  also  any  resin,  see  later,  7)  remains  in  solution.     The  solution  is  then 
filtered  and  the  filtrate  diluted  with  a  large  amount  of  water.      With  the 
pure  wax  the  liquid  remains  clear,  whereas  the  presence  of  stearine  (about 
i%  or  more)  produces  a  marked  turbidity  or  a  white  precipitate,  which 
may  be  collected  and  identified  by  means  of  its  melting  point   (53-55°) 
and  saponification  number  (about  195),  provided  of  course  that  Morawski's 
reaction  indicates  that  resin  is  absent. 

i,-When  resin  and  other  extraneous  acid  substances  soluble  in  alcohol  are 
absent,  the  stearine  (S)  added  to  a  wax  may  be  calculated  from  the  acid 
number  found  (a)  by  means  of  the  formula  : 

Q   _  ioo(a  —  20) 

O     —  . 

175 

When  a  wax  or  a  mixture  resembling  wax  contains  stearic  acid  and 
resin,  it  is  well  to  eliminate  these  substances  immediately  by  means  of  85% 
alcohol  and  co  make  the  other  tests  and  determinations  on  the  insoluble 
residue. 

7.    Resin  (Colophony). — From  3  to  4  grams  of  the  wax  are  heated 
with  dilute  alcohol  (about  80%),  the  mass  being  allowed  to  cool  and  filtered, 


436  BEESWAX 

the  filtrate  evaporated  and  the  residue  employed  for  the  detection  of  resin 
by  means  of  acetic  anhydride  and  sulphuric  acid  (see  General  Methods, 
20). 

The  quantitative  .determination  may  be  effected  by  Twitchell's  method 
(see  General  Methods,  20). 

8.  Paraffin  Wax  and  Ceresine. — As  a  preliminary  test,  5  grams  of 
the  wax,  about  25  c.c.  of  seminormal  alcoholic  potassium  hydroxide  and 
20  c.c.  of  95%  alcohol  are  boiled  for  an  hour  in  a  reflux  apparatus  over  a 
naked  flame  :  with  pure  wax  the  solution  is  clear,  or  almost  clear,  and  remains 
so  when  diluted  with  hot  water,  but  with  wax  mixed  with  paraffin  wax 
or  ceresine,  the  liquid  remains  turbid,  and  becomes  still  more  so  when  diluted 
with  water.1 

A  more  certain  and  even  quantitative  test  may  be  made  by  Leys' 
method  2  :  10  grams  of  the  wax,  25  c.c.  of  alcoholic  potash  (45  grams 
KOH  per  litre  of  absolute  alcohol)  and  50  c.c.  of  pure  benzene  are  boiled 
for  20  minutes  in  a  reflux  apparatus  on  an  asbestos  card  over  a  naked  flame, 
50  c.c.  of  water  being  then  added  and  the  boiling  continued  for  10  minutes. 
After  a  short  rest,  the  liquid  separates  into  two  layers  :  an  upper,  clear, 
yellowish  one  (benzene  solution  of  higher  alcohols  and  hydrocarbons)  and 
a  lower,  somewhat  opalescent  one  (aqueous-alcoholic  soap  solution).  As 
soon  as  the  separation  is  sharp,  the  lower  hot  liquid  is  drawn  off  and  replaced 
by  50  c.c.  of  hot  water,  and  the  liquid  boiled  for  10  minutes  with  a  reflux 
apparatus.  The  aqueous  solution  is  then  immediately  withdrawn  and 
the  benzenic  liquid  transferred  to  a  tared  capsule,  the  various  vessels  in 
which  the  operations  have  been  conducted  being  washed  out  with  hot 
benzene  3  ;  the  solvent  is  then  evaporated  on  the  water-bath  and  the  residue 
dried  at  100°  and  weighed.  This  gives  the  total  weight  of  higher  alcohols 
and  hydrocarbons  contained  in  the  wax  and  from  this  the  content  of  extrane- 
ous hydrocarbons  may  be  deduced,  knowing  that  in  pure  wax  the  sum  of 
alcohols  and  hydrocarbons  never  exceeds  55%  (usually  oscillating  about 

50%). 

If  desired,  the  hydrocarbons  may,  according  to  Leys,  be  separated 
quantitatively  from  the  higher  alcohols  by  means  of  a  mixture  of  amyl 
alcohol  and  cone,  hydrochloric  acid,  in  which  the  latter  dissolve  (see  original 
paper)  ;  or,  as  Buchner  recommends,4  the  acetyl  number  (see  General 
Methods,  n)  of  the  mixed  higher  alcohols  and  hydrocarbons  may  be  deter- 
mined and  the  quantity  of  the  former  deduced  by  taking  122  as  the  mean 
acetyl  number  of  the  higher  alcohols  of  the  pure  wax. 

9.  Test  for   Carnauba   Wax   and    Insect   or   Chinese   Wax. — No 
special  reactions  exist  for  identifying  these  waxes  in  beeswax   ;  when,  how- 
ever, the  presence  of  other  extraneous  substances  has  been  excluded  and 
any  stearic  acid  and  resin  eliminated  as  indicated  above  (6),  their  presence 
may  be  presumed  from  increase  of  the  specific  gravity,   melting  point, 

1  Werder  :    Monit.  scient.,   1901,  p.   127. 

2  Journ.  de  Pharm.  et  Chim.,   1912,  V,  p.  577. 

3  Very  suitable  for  this  purpose  is  a  special  vessel   (Boule  a  decantation  chaude) 
devised  by  Leys  and  consisting  of  a  tapped  funnel  flattened  on  one  side  so  that  it  may 
be  heated  like  an  ordinary  flask. 

4  Zeitschr.  f.  offentl.  Chem.,  1913,  p.  447. 


BEESWAX 


437 


refractivity  and  ratio  value  (see  above)  and  from  diminution  in  the  acid 
number  (see  later). 

10.  Test  for  Japan  Wax  (from  various  species  of  Rhus),  Tallow 
and  other  Fats  in  general. — A  scrap  of  fused  potassium  bisulphate  is 
added  to  about  i  gram  of  the  molten  wax  in  a  test-tube  and  the  mixture 
strongly  heated  over  a  direct  flame  :  the  pure  wax  gives  pungent  sulphurous 
fumes,  whereas  in  presence  of  fats  (glycerides)  the  characteristic  irritating 
odour  of  acrolein  (due  to  decomposition  of  the  glycerine)  is  observed  and 
a  strip  of  filter-paper,  soaked  in  a  solution  of  sodium  nitroprusside  and 
a  little  piperidine  and  placed  at  the  mouth  of  the  tube,  turns  violet- 
blue. 

If  this  test  shows  the  presence  of  glycerides,  the  glycerine  is  determined 
as  in  General  Methods,  17  ;  the  amount  of  glycerine,  multiplied  by  10,  gives 
approximately  the  quantity  of  fatty  substance  in  the  wax,  since  fats  contain 
on  the  average  about  10%  of  glycerine. 

It  should  also  be  borne  in  mind  that  Japan  wax,  tallow  and  other  fats 
lower  the  melting  point  and  raise  the  saponification  number  (tallow  raises 
also  the  iodine  number)  of  the  wax  (see  later). 

11.  Detection  of  Wool -Fat  and  its  Products  (Wool -Fat  Stearine 
or  Wax). — The  higher  alcohols  and  hydrocarbons  are  extracted  from  the 
wax  by  Leys'  method  (8),  the  mixture  thus  extracted  being  tested  for 
cholesterol  by  means  of  chloroform  and  sulphuric  acid  (see  General  Methods, 
19,  Higher  Alcohols). 

12.  Determination  of  the  Water  and  Various  Extraneous  Im- 
purities.— About  5  grams  of  the  wax  as  it  stands  are  heated  at  100-105° 
to  constant  weight,  the  loss  representing  the  water.     The  residue  is  dis- 
solved in  hot  benzene  and  the  solution  filtered  from  any  appreciable  undis- 
solved  portion  through  a  tared  filter,  the  insoluble  matter  being  washed 
well  with  hot  benzene,  dried  at  100°  and  weighed. 

The  residue  insoluble  in  benzene  is  then  tested  for  starchy  or  mineral 
matters  by  the  usual  methods. 

13.  Extraneous  Colouring  Matters. — About  a  gram  of  the  rasped 
wax  is  shaken  with  ammonia  :    in  presence  of  turmeric,  a  reddish-brown 
coloration  is  obtained. 

To  detect  coal-tar  dyes,  the  wax  is  extracted  with  90-95%  alcohol  in 
the  hot.  The  liquid  is  then  cooled  well  at  15°  for  some  hours  and  filtered, 
the  filtrate  being  evaporated  and  tested  for  artificial  colouring  matters  (see 
Coal-tar  Dyes  in  Vol.  II).  As  a  rule  imitation  wax  and  wax  substitutes 
are  coloured  with  the  so-called  Soudan  dyes,  which  are  turned  pink  with 
cone,  hydrochloric  acid. 

14.  Detection  of  Beeswax  in  Mixtures  with  other  Substances. — 
To  ascertain  if  wax  is  contained  in  wares  of  different  kinds,  such  as  paraffin 
wax,  fats,  candles,  artificial  fruit  and  flowers,  lithographic  stones,  mastics, 
encaustics,  ointments,  plasters,  waxed  paper  and  cloth,  myricyl  alcohol  is 
tested  for.     This  may  be  done  indirectly  by  means  of  the  acetyl  number, 
or  by  transforming  the  alcohol  into  melissic  acid.     The  test  is,  however, 
practicable  only  when  other  substances  containing  higher  alcohols,  such  as 
wool-fat  and  its  products,  are  excluded.     Carnauba  wax,  which  also  con- 


4sS  BEESWAX 

tains  myricyl  alcohol,  behaves  like  beeswax,  and  the  same  holds  with  Chinese 
insect  wax,  which  contains  ceryl  alcohol. 

(a)  BY  MEANS  OF  THE  ACETYL  NUMBER.     The  substance  *  is  saponified 
and  the  unsaponifiable  part  extracted  by  the  usual  methods  or  preferably 
by  Leys'  method  (see  8)  and  its  acetyl  number  determined  (see  General 
Methods,  n).     If  this  number  is  found  to  be  zero,  the  presence  of  the  wax 
May  be  excluded ;   if,  however,  there  is  an  acetyl  number,  the  presence  of 
the  wax  may  be  assumed  and  the  amount  may  be  calculated  approximately 
from  the  fact  that  the  mean  acetyl  number  of  the  higher  alcohols  of  the 
wax  is  122  and  that  the  wax  contains,  on  the  average,  about  40%  of  higher 
alcohols. 

(b)  BY    TRANSFORMATION    OF    THE    MYRICYL    ALCOHOL    INTO     MELISSIC 

ACID.  5  grams  of  unsaponifiable  substance,  extracted  as  for  the  pre- 
ceding test,  are  intimately  mixed  with  about  10  grams  of  powdered  soda 
lime  and  a  little  caustic  soda,  the  mixture  being  placed  in  a  large  test-tube 
and  this  plunged  into  a  sand-bath  and  heated  to  200-220°  for  2  hours  ; 
the  temperature  is  measured  with  a  thermometer  immersed  in  the  substance 
and  used  at  intervals  as  a  stirrer.  When  cold,  the  substance  is  extracted 
with  petroleum  ether,  the  solvent  evaporated  and  the  residue  weighed. 
If  the  weight  is  equal  or  nearly  equal  to  that  of  the  substance  used,  the 
presence  of  wax  is  excluded,  but  if  the  petroleum  ether  extract  is  appreciably 
less  in  weight  than  the  substance  taken,  wax  may  be  present.  In  the 
latter  case  the  difference  between  5  grams  (weight  of  substance  used)  and 
the  weight  of  the  residue  represents  the  myricyl  alcohol  contained  in  the 
5  grams  of  unsaponifiable  matters.  If,  then,  the  percentage  of  unsaponi- 
fiable matter  in  the  substance  is  known,  the  myricyl  alcohol  contained  in 
100  parts  of  the  substance  itself  and  hence  approximately  the  percentage 
of  the  wax  present  may  be  calculated,  since  38  parts  of  myricyl  alcohol 
correspond  on  the  average  with  100  parts  of  beeswax. 

* 
*  * 

The  purity  of  a  wax  is  judged  first  of  all  from  the  results  of  the  determina- 
tions of  the  various  characters,  account  being  naturally  taken  of  the  origin 
and  nature  of  the  wax  :  if  all  or  some  of  these  characters  lie  outside  the  limits 
indicated  in  Table  XLIX,  the  wax  is  not  genuine. 

A  low  specific  gravity  indicates  the  presence  of  solid  paraffin  or  ceresine, 
stearic  acid  or  tallow,  and  a  high  one  that  of  carnauba  wax,  Japan  wax  or  colo- 
phony. 

The  acid,  saponification,  ester,  ratio,  iodine  and  refractometric  numbers 
are  also  influenced  more  or  less  by  the  presence  of  various  foreign  substances, 
as  is  shown  in  the  following  table  (page  439),  where  the  mean  characters  of 
ordinary  virgin  wax  are  compared  with  those  of  the  substances  most  usually 
employed  to  adulterate  it. 

It  should,  however,  be  noted  that  mixtures  may  be  prepared,  with  or  without 
beeswax,  so  as  to  have  the  characters  given  above  for  the  pure  wax.  Con- 
sequently, if  it  is  certain  that  a  wax  is  adulterated  if  its  characters  are  abnormal, 
normal  characters  do  not  necessarily  correspond  with  a  pure  wax  ;  in  the  latter 
case,  tests  6-n  must  be  carried  out. 

1  In  the  case  of  plasters  or  waxed  paper  or  cloth,  the  sample  is  extracted  with 
boiling  benzene,  the  liquid  filtered  and  evaporated  and  the  residue  examined. 


WOOL  FAT 


439 


Specific 
Gravity 
at  15°  C. 

Melting 
Point 

Acid 
Number 

Saponi- 
fication 
Number 

Ester 
Number 

Ratio 
Value 

Iodine 
Number 

Refracto- 
metric 
Degree  at 

40°  C. 

a 

b 

c 

A 

e 

/ 

g 

ft 

Beeswax 

0-964 

63° 

20 

95 

75 

370 

10 

44 

Insect  wax  . 

0-970 

82° 

0 

63 

63 

63 

— 

46 

Carnauba  wax  . 

o  -995 

85° 

4 

79 

75 

18-75 

10 

66 

Japan  wax  . 

0-990 

53° 

20 

220 

200 

IO 

9 

47 

Stearine  . 

— 

below  55° 

195 

195 

0 

0 

.  — 

•  — 

Tallow    . 

0-948 

42° 

4 

195 

191 

48 

40 

47 

Resin  (colophony) 

I  -ICO 

above  70  °i  180 

IOX) 

10 

0-06 

U5 

— 

Solid  paraffin    . 

0-870 

below  65° 

0 

0 

0 

o 

0 

22 

Ceresine  . 

0-920 

above  60° 

0 

0 

0 

o 

o 

40 

WOOL    FAT 

This  is  obtained  from  wool  by  washing  with  soap  or  alkali  carbonate 
solution  or  by  extracting  with  a  solvent  (carbon  disulphide  or  benzine). 

The  crude  fat  is  utilised  especially  for  the  preparation  of  lanoline  and 
distilled  wool  fat,  from  which  wool  fat  oleine  and  stearine  are  prepared. 
The  latter  products  are  dealt  with  in  the  next  chapter  (Industrial  Products 
from  the  Treatment  of  Fatty  Matters)  ;  here  we  shall  deal  only  with  crude 
and  purified  wool  fat  and  lanoline. 

A.    Crude  Wool  Fat 

This  has  a  tallowy  consistency,  a  yellow  or  brown  colour,  and  a  peculiar, 
disgusting  odour.  It  is  slightly  soluble  in  alcohol,  and  more  so  in  ether, 
chloroform,  benzene,  etc.  •  it  saponifies  with  difficulty.  Its  physical  and 
chemical  characters  are  given  later  in  Table  XLIX,  dealing  with  animal 
waxes.  It  is  dextro-rotatory  ([a]l5°  =  about  6-9°  in  chloroform  solution), 
and  its  acid  number  may  vary  from  about  10  to  50  (5-25%  of  free  acids 
calculated  as  oleic  acid)  according  to  the  method  used  in  its  extraction. 
On  calcination  it  leaves  little  ash  (1-5%). 

It  contains  marked  quantities  of  unsaponifiable  substances  (40-50%), 
consisting  mainly  of  cholesterol  and  isocholesterol,  and  consequently  gives 
the  reaction  of  these  higher  alcohols  with  chloroform  and  sulphuric  acid 
(see  General  Methods,  19,  i,  Higher  Alcohols).  It  may  also  contain  water 
and  various  foreign  impurities  in  varying  quantities. 

Crude  wool  fat  is  readily  identified  by  its  external  characters  and  by 
the  cholesterol  reaction.  In  analysing  it,  it  is  usually  sufficient  to  determine 
the  content  of  water,  extraneous  impurities,  and  ash,  with  possibly  the 
acid  number  and  the  unsaponifiable  matter,  by  the  usual  methods  (see 
General  Methods). 

B.     Purified  Wool  Fat  (Lanoline) 

Purified  wool  jat  is  pale  yellow  and  sticky,  has  a  faint,  peculiar  smell 
and  the  consistency  of  an  ointment  and  undergoes  little  change  in  the  air. 


440  SPERMACETI 

It  gives  stable  mixtures  or  emulsions  with  large  quantities  of  water  (up  to 
more  than  100%),  and  the  fat  mixed  with  20-30%  of  water  is  given  the 
name  Lanoline.  \ 

It  dissolves  little  in  cold  alcohol  and  somewhat  more  in  boiling  absolute 
alcohol ;  it  is  soluble  in  ether  or  chloroform,  giving,  however,  turbid  liquids 
when  it  contains  water.  Its  characters  are  indicated  in  Table  XLIX. 

When  a  solution  of  o-i  gram  of  dehydrated  lanoline  in  5  c.c.  of  chloroform 
is  carefully  poured  on  to  5  c.c.  of  cone,  sulphuric  acid,  at  the  zone  of  contact 
of  the  two  liquids  there  is  produced  a  bright  brownish-red  coloration,  which 
reaches  its  maximal  intensity  after  24  hours. 

The  most  important  tests  to  be  made  on  lanoline,  especially  that  for 
pharmaceutical  purposes,  are  :  t^ 

1.  Water  and  Ash.— 10  grams  are  heated   at  100-110°  to   constant 
weight,  the  residue  being  carefully  incinerated  and  the  ash  weighed. 

2.  Acidity.— As  in  General  Methods,  7. 

According  to  the  Official  Italian  Pharmacopoeia,  the  test  for  acidity  is 
made  by  dissolving  2  grams  of  the  lanoline  in  20  c.c.  of  petroleum  ether, 
adding  2  drops  of  phenolphthalein  solution  and  then  0-5  c.c.  of  decinormal 
sodium  hydroxide  solution  :  the  liquid  should  be  coloured  a  persistent  red. 

3.  Other  Tests. — -The  lanoline  is  heated  with  aqueous  caustic  soda 
solution  to  ascertain  if    ammonia  is  evolved.     10    grams  of    lanoline  are 
heated  on  the  water- bath  with  50  grams  of  water  :    a  clear  and  slightly 
coloured  layer  of  fused  fat  should  form  at  the  surface  of  the  water  ;    with 
impure  lanoline  a  brown,  turbid  and  frothy  mass  is  obtained. 


*** 


Pure  anhydrous  lanoline  should  contain  only  traces  of  moisture,  and  that 
emulsified  with  water  should  contain  not  more  than  30%  of  the  latter.  Further, 
it  should  have  little  ash  (at  most  0-05%),  give  no  acid  reaction  with  litmus 
paper,  correspond  with  the  Official  Italian  Pharmacopoeia  test  (2),  and  give 
no  ammonia  when  heated  with  soda  solution. 

Spermacetis 

This  is  the  solid  portion  obtained  by  cooling  and  pressure  from  the 
oil  contained  in  the  cephalic  cavity  of  the  sperm  whale  or  cachalot  (Catodon 
macrocephalus)  and  allied  species.  f 

Refined  or  pure  spermaceti  of  commerce  is  in  white,  hard,  crystalline 
masses  (thin  sheets),  slightly  fatty  to  the  touch  and  almost  odourless  ;  in 
the  air  it  becomes  yellowish  and  rancid. 

It  dissolves  in  boiling  alcohol,  from  which  it  crystallises  on  cooling,  and 
it  is  soluble  also  in  ether,  chloroform,  benzene  and  carbon  disulphide  ;  it 
dissolves  very  slightly  in  cold  98%  alcohol  and  is  insoluble  in  90%  alcohol 
or  in  water.  Its  physical  and  chemical  characters  are  given  in  Table  XLIX. 

Spermaceti  consists  mostly  of  cetin  (the  cetyl  ester  of  palmitic  acid), 
m.pt.  53-5°,  and  contains  50-52%  of  unsaponifiable  substances. 

Detection  of  Adulterants.- — Additions  of  ceresine  or  solid  paraffin, 
stearic  acid  (stearine),  tallow  and  beeswax  are  made,  but  only  rarely,  since 
extraneous  substances  easily  destroy  the  characteristic  crystalline  structure. 


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441 


442  SPERMACETI   OIL 

The  purity  of  a  spermaceti  is  judged  from  its  melting  point,  acid  and 
saponification  numbers  and  the  amount  of  unsaponifiable  matter  (see  General 
Methods,  4,  7,  8  and  19).  Addition  of  stearine  or  wax  gives  an  acid  number, 
while  that  of  tallow  or  other  fat  increases  the  saponification  number  ;  solid 
paraffin  or  ceresine  lowers  the  saponification  number  and  increases  the 
amount  of  unsaponifiable  matter. 

The  two  following  tests  are  prescribed  by  the  Official  Italian  Pharma- 
copoeia : 

1.  SOLUBILITY  IN  BENZENE,     i  gram  of  the  spermaceti  is  dissolved 
in  3  grams  of  benzene  at  a  gentle  heat  :  on  cooling  the  liquid  should  remain 
clear. 

2.  TEST  FOR  STEARIC  ACID,     i  gram   is   boiled   with    50  c.c.  of  90% 
alcohol  and  i  gram  of  dry  sodium  carbonate,  and  filtered  :    the  filtrate, 
when  acidified  with  a  dilute  acid,  should  become  barely  opalescent,  any 
precipitate  indicating  the  presence  of  stearic  acid. 


* 
*  * 


According  to  the  Official  Italian  Pharmacopoeia,  pure  spermaceti  should 
have  no  odour  of  fish,  should  have  a  specific  gravity  0-940-0-950,  and  should 
melt  at  50-54°  or,  if  recrystallised  from  alcohol,  at  54-55°  ;  the  alcoholic  solu- 
tion should  not  have  an  acid  reaction  ;  tests  i  and  2  should  be  fulfilled. 

SPERMACETI    OIL 

This  is  the  liquid  part  of  the  oil  contained  in  the  cephalic  cavity  of  the 
cachalot  and  allied  species. 

The  ordinary  refined  spermaceti  oil  of  commerce  is  an  almcst  colourless 
or  pale  yellow  liquid,  mobile  and  nearly  odourless. 

It  is  a  liquid  wax,  consisting  mostly  of  esters  of  one  or  more  higher 
alcohols  with  fatty  acids  of  the  oleic  acid  series  (fisetoleic  acid).  It  con- 
tains 37-45%  of  higher  alcohols  (unsaponifiable  substances)  and  about  60% 
of  fatty  acids  combined  with  these  alcohols  ;  it  contains  also  very  small 
quantities  (0-1-0-4%)  of  free  acids  and  it  turns  rancid  with  great  difficulty. 
Its  characters  are  shown  in  Table  XLIX. 

Detection  of  Adulterations. — Adulteration  with  mineral  oils  or  fatty 
oils  is  common.  These  may  be  detected  by  determining  the  specific  gravity, 
saponification  and  iodine  numbers,  and  unsaponifiable  substances,  bearing 
in  mind  the  following  : 

1.  MINERAL  OILS.     These  lower  the  saponification  number  and  increase 
the  content  in  unsaponifiable  substances.     If  the  latter  are  boiled  with 
acetic  anhydride  and  then  cooled,  the  mineral  oils  separate  almost  com- 
pletely from  the  liquid  (see  General  Methods,  19). 

2.  FATTY  OILS.     These  raise  the  specific  gravity  and  the  saponification 
number  and  diminish  the  proportion  of  unsaponifiable  substances.     They 
may  be  recognised  by  the  presence  of  glycerine  as  indicated  under  Beeswax, 
10. 


CHAPTER  X 

INDUSTRIAL  PRODUCTS 
FROM    THE    TREATMENT    OF    FATTY    MATTERS 

The  most  important  industrial  products  obtained  from  the  treatment 
of  fatty  matters  are  :  boiled  linseed  oil,  oxidised  oils,  hardened  or  hydro- 
genised  oils,  Turkey-red  oils,  oleine,  stearine,  candles,  soap  and  glycerine. 

The  methods  of  analysis  used  for  these  materials  are  largely  those  em- 
ployed with  fatty  substances,  being  based  mainly  on  the  determinations 
of  the  various  characters  (specific  gravity,  melting  point,  acid  number, 
saponification  number,  iodine  number,  etc.),  for  which  the  general  methods 
of  the  preceding  chapter  are  used.  Any  special  tests  necessary  are  described, 
as  occasion  offers,  in  the  following  articles. 

BOILED    LINSEED    OIL 

Boiled  linseed  oil  is  fluid  but  more  viscous  than  the  crude  oil,  and  is 
more  or  less  brownish-yellow  or  brown  and  of  a  peculiar  odour  ;  there  is 
also  a  very  thick,  almost  pasty  form,  which  is  brown  with  a  greenish  fluores- 
cence and  has  a  very  marked  odour. 

In  general,  the  boiled  oil  is  distinguished  from  the  ordinary  or  crude 
form  by  the  appearance,  the  smell,  the  high  specific  gravity  (0-937-0-99), 
the  presence  of  drying  agents  (these  are  sometimes  absent,  in  which  case 
the  distinction  is  readily  made  by  other  characters)  and  especially  by  the 
ease  with  which  it  dries. 

Boiled  linseed  oil  may  be  found  mixed  or  adulterated  with  resin,  resin 
oil,  mineral  oil,  fish  or  blubber  oil,  or  vegetable  oil  (colza,  soja  bean,  etc.). 
Its  analysis  includes  the  following  determinations  and  tests  : 

1.  Specific    Gravity,    Iodine    Number,    Saponification    Number, 
Acid  Number. — By  the  general  methods  given  in  the  preceding  chapter. 

2.  Detection  of  Extraneous  Oils. — As  in  ordinary  linseed  oil  (see  p. 

404). 

3.  Detection  of  Unsaponifiable  Substances  and  Volatile  Oils. — 

A  few  grams  of  the  oil  are  saponified  with  alcoholic  potash  in  the  usual 
way  and  then  diluted  with  2-3  vols.  of  water  :  if  the  oil  is  pure  the  solution 
is  clear  or  contains  a  few  flocks  of  lead  or  manganese  hydroxide  if  dryers  are 
present,  but  a  turbid  liquid  is  obtained  if  the  oil  contains  mineral  or  resin  oils. 

443 


444  BOILED   LINSEED   OIL 

If  the  oil  is  distilled  in  a  current  of  steam,  the  distillate  will  contain  any 
oil  of  turpentine  or  benzine  present. 

The  unsaponifiable  substances  may  be  determined  quantitatively  by 
the  methods  described  on  p.  388. 

4.  Detection  of  Resin. — The  oil  is  shaken  with  an  equal  volume  of 
about  70%  alcohol,  the  alcoholic  liquid  being  then  separated  and  evaporated, 
and  the  residue  tested  by  means  of  Morawski's  reaction  (see  p.  390). 

Oils  boiled  with  resinates  naturally  contain  small  quantities  of  resin 
due  to  the  dryer.  Addition  of  resin  should  be  assumed  only  when  the 
alcoholic  extract  is  large  in  amount  and  the  acid  number  of  the  oil  is  high 
(at  least  above  12  ;  see  later). 

5.  Detection  of  Siccatives. — This  may  be  made  on  the  ash  of  the  oil 
or  by  dissolving  the  oil  in  ether  and  shaking  with  dilute  nitric  acid,  the 
nitric  acid  solution  being  tested  by  the  ordinary  methods  for  lead,  man- 
ganese, calcium,  zinc  and  cobalt. 

6.  Drying  Properties. — A  drop  of  the  oil  is  spread  uniformly  on  a 
glass  plate  (5  X  10  cm.)  and  left  in  the  air,  protected  from  direct  sunlight, 
at  15-20°.     From  time  to  time  the  course  of  the  drying  is  tested  by  pressing 
the  oily  layer  hard  with  the  finger  :    drying  is  complete  when  the  finger 
no  longer  adheres  to  the  surface.     The  latter  is  then  heated  to  100°  to  see 
if  cracking  occurs. 

Further,  25  parts  of  the  oil  are  mixed  intimately  with  20  parts  of  zinc 
white  or  minium,  the  paste  thus  obtained  being  spread  uniformly  on  an 
iron  plate  and  left  to  dry  as  before. 

*** 

Good  boiled  linseed  oil  should  satisfy  the  following  requirements  : 

That  boiled  at  a  moderate  temperature  should  be  only  slightly  coloured 
and  should  yield  a  perfectly  white  paste  when  mixed  with  pure  lead  or  zinc 
white. 

Its  specific  gravity  should  not  be  below  0-935  and  as  a  rule  lies  between 
0-935  and  0-948,  but  oil  heated  at  a  very  high  temperature  (double  boiled, 
burned)  may  have  a  value  as  high  as  0-99.  The  presence  of  extraneous  oils 
(vegetable,  animal,  mineral)  lowers  the  specific  gravity. 

The  iodine  number  may  vary  from  150  to  172  in  light  boiled  oils,  but  may 
fall  to  .70°,  with  those  strongly  boiled  and  dense. 

The  saponifi cation  number  should  lie  between  190  and  195,  and  is  lowered 
by  colza  oil  and  especially  by  mineral  or  resin  oil. 

The  acid  number  should  not  exceed  12  (usually  it  stands  between  7  and  10) 
and  is  raised  by  free  resin. 

It  should  not  contain  foreign  oils  or  free  resin. 

The  content  of  unsaponifiable  substances  should  not  exceed  2%  at  the  most. 

The  amount  of  dryer  should  be  such  that  the  oil  does  not  leave  more  than 
i%  of  ash. 

In  the  drying  test,  pale  oils  should  dry  completely  within  20  hours  and  dark 
ones  within  12  hours.  After  being  heated  at  100°,  the  dry  layer  should  not 
exhibit  cracking  and  should  become  detached  in  scales  when  scraped  with  a 
knife.  When  mixed  with  zinc  white  or  minium,  it  should  dry  completely  within 
24  hours. 


OXIDISED   OILS   (BLOWN   OILS)  445 


OXIDISED    OILS 
(Blown  Oils) 

These  are  obtained  by  passing  a  current  of  air  through  a  fatty  oil  at  a 
temperature  of  about  70-120°  until  the  oil  becomes  thick  and  viscous  like 
castor-oil.  Colza,  cottonseed,  maize,  foot  and  fish  oils  are  usually  employed 
for  this  purpose. 

In  general,  blown  oils  are  dense,  viscous,  reddish-brown  liquids  with  a 
special  odour  (of  boiled  oil) .  In  comparison  with  the  corresponding  original 
oils,  they  have  high  specific  gravities,  refractivities  and  saponification 
numbers  and  low  iodine  numbers  (see  Table,  p.  446).  Further,  they  contain 
marked  quantities  of  hydroxy- acids,  and  it  is  characteristic  of  them  that 
they  furnish  deep  brown  fatty  acids  (almost  black  with  blown  fish  oik), 
only  partially  soluble  in  ether. 

Analysis  of  these  products  is  concerned  principally  with  the  two  following 
cases  : 

1.  Origin  of  the  Blown  Oil. — It  is  somewhat  difficult  to  state  the 
nature  of  the  original  oil  from  which  a  blown  oil  is  prepared,  since  the  specific 
colour  reactions   no   longer  hold.     An  approximate   orientation  may  be 
obtained  by  means  of  the  following  criteria. 

The  fatty  acids  of  oxidised  colza  oil  are  liquid  and  their  lead  salts  are 
mostly  soluble  in  ether. 

The  fatty  acids  of  oxidised  cottonseed  oil  are  solid  and  their  lead  salts 
partially  soluble  in  ether. 

The  fatty  acids  of  oxidised  fish  oils  are  blackish  and  saponification  of 
these  oils  yields  a  black,  pitchy  substance  insoluble  in  potash,  alcohol  or 
ether  and  similar  to  the  linoxyn  of  linseed  oil.  This  does  not  occur  with 
blown  vegetable  or  foot  oils.  Blown  fish  oils  are  the  ones  showing  the 
greatest  density  accompanied  by  the  highest  iodine  number. 

Oxidised  foot  oils  exhibit  a  specific  gravity  equal  to  that  of  oxidised 
vegetable  oils  but  a  less  iodine  number. 

2.  Mixtures  of  Blown  Oils  with  Mineral  Oils. — Mixtures  of  heavy 
mineral  oil  and  oxidised  oil  (about  5-30%)  form  good  lubricants  for  marine 
engines. 

Such  products  are  recognisable  by  the  smell  and  by  the  following  test  : 
10  grams  of  the  oil  are  saponified  with  25  c.c.  of  alcoholic  potash  in  the 
usnal  way,  heating  for  half  an  hour  on  the  water-bath  in  a  reflux  apparatus 
with  frequent  shaking.  Without  evaporating  the  alcohol,  the  whole  is 
transferred  to  a  separating  funnel,  diluted  with  150  c.c.  of  water,  shaken 
gently  and  carefully  and  left  to  stand  until  sharp  separation  into  two  layers 
takes  place,  the  lower  aqueous  layer  being  then  run  off  and  the  supernatant 
mineral  oil  collected  separately  (with  the  help  of  a  little  ether),  dried  and 
weighed. 

On  the  other  hand,  the  aqueous  liquid  is  acidified  and  the  fatty  acids 
separated  :  these  should  exhibit  the  characters  of  the  acids  of  oxidised 
oils,  that  is,  they  should  be  brown  and  not  completely  soluble  in  ether 
(see  above). 


446 


HARDENED   OR  HYDROGENISED   OILS 


Examples  of  the  characters  of  blown  oils  in  comparison  with  those  of 
the  corresponding  original  oils,  are  as  follows  : 


Zeiss 

Hydroxy- 

butyro- 

acids 

Specific  gravity 

refracto- 

Saponifi- 
cation. 

Iodine       insoluble 

at  15°. 

meter 

Number.            in 

Number 

Number. 

petroleum 

at  15°. 

ether,  %. 

Colza  oil 

(  ordinary    . 
(blown  . 

0-912-0-917 
0-967-0-977 

68-69 
80 

i 
170-181 
197-268  j 

94-106 
46-65 

o 

20-28 

Cottonseed  o 

.,  (ordinary    . 
il-L  , 
(blown  . 

0-922-0-925 
0-972-0-979 

68 
80  -8  1 

191-198 
213-226 

107-110 
50-66 

o 
26-29 

Ox-foot  oil 

j  ordinary    . 
(blown  . 

0-921 
0-972 

62 
73-74 

194 
241-242 

71 

33 

TTi  cT~i   01  1 

(ordinary    .           0-925 

78 

190-191 

134 

— 

_L  loll    Wll 

(blown  . 

0-980-0-985 

90-91 

247-248  j 

73-74 

HARDENED    OR    HYDROGENISED    OILS 

These  are  obtained  by  subjecting  liquid  fatty  oils,  either  vegetable  or 
animal,  to  the  action  of  hydrogen  at  a  temperature  of  130-140°  in  presence 
of  a  catalytic  substance,  usually  finely  divided  reduced  nickel,  or  palladium, 
platinum  and  various  metallic  oxides.  The  unsaturated  liquid  fatty  acids 
(oleic,  linoleic,  etc.)  of  the  glycerides  of  the  oils  are  transformed  into  solid 
stearic  acid,  so  that  the  oils  themselves  become  solid. 

These  products,  marketed  under  the  names  of  Talgol,  Candelite,  Coryphot, 
are  usually  obtained  by  hydrogenising  marine  animal  oils  (in  particular, 
whale  oil),  but  they  may  also  be  prepared  from  vegetable  oils  (cottonseed, 
soja-bean,  castor,  etc.). 

As  a  rule,  hardened  fats  are  solid  and  of  the  consistency  of  tallow  (with 
very  prolonged  hydrogenation  they  acquire  the  hardness  of  waxes)  and 
they  have  persistent  colours,  odours  and  tastes  which  are  similar  to  those 
of  tallow  but  no  longer  recall  the  original  oils.  They  usually  melt  at  40-50°, 
but  the  strongly  hydrogenised  ones  have  still  higher  melting  points.  Their 
fatty  acids  melt  at  temperatures  2-3°  below  the  points  of  fusion  of  the 
neutral  fats.  Their  acid  number  is  small  and  their  saponification  number 
normal  (190-195),  while  the  iodine  number  depends  on  the  degree  of  hydro- 
genation and  may  fall  to  a  few  units. 

Hydrogenised  oils  give  the  general  colour  reactions  of  the  original  oils 
very  similarly  to  the  latter  :  thus,  they  give  Hauchecorne's,  Heydenreich's 
and  Bellier's  reactions  if  they  are  derived  from  vegetable  oils  and  Tortelli 
and  Jaffe's  reaction  if  from  marine  animal  oils.  They  do  not,  however 
give  Halphen's  octabromide  reaction  for  marine  animal  oils  (see  p.  428)  or 
Halphen  and  Milliau's  reactions  for  cottonseed  oil  ;  but  partially  hydro- 
genised cottonseed  oil,  even  when  solid,  still  gives  Halphen's  reaction  quite 
distinctly. 

Hydrogenised   oils   contain   unchanged   the   unsaponifiable   substances 


TURKEY-RED   OIL  447 

(phytosterol  or  cholesterol)  of  the  original  oils  and,  as  a  rule,  traces  of  the 
catalyst  (mostly  nickel)  are  found. 

The  analysis  of  these  products  includes  : 

1.  Characters  and  Origin. — Of  the  characters  of  hardened  oils,  those 
of  special  importance,  besides  the  objective  ones,  are  the  melting  point, 
solidifying  point  of  the  fatty  acids  (titer)  and  the  acid,  saponification  and 
iodine  numbers. 

To  ascertain  the  origin  of  a  hardened  oil,  the  unsaponifiable  substances 
(sterols)  must  be  extracted  and  identified  (see  Hog's  Fat)  :  hardened  animal 
oils  contain  cholesterol  and  the  vegetable  ones,  phytosterol. 

The  Tortelli  and  Jaffe  reaction  (see  p.  430)  indicates  if  a  hardened  oil 
is  prepared  from  a  marine  animal  oil. 

2.  Test  for  Traces  of  Catalyst  (Rickel).— This  may  be  made  on  the 
ash  of  the  product  or,  according  to  Fortini,  in  the  following  way  : 

5  to  10  grams  of  the  fat  are  heated  for  half  an  hour  on  the  water- 
bath  with  as  much  cone,  hydrochloric  acid,  with  frequent,  vigorous  shaking  ; 
the  acid  is  then  filtered  through  a  moist  filter  into  a  dish,  evaporated  to 
dryness,  and  the  residue  moistened  with  a  few  drops  of  i%  alcoholic  dimethy- 
glyoxime  solution  :  in  presence  of  nickel  a  red  coloration  is  obtained,  this 
being  rendered  more  evident  when  the  solution  is  made  slightly  alkaline 
with  a  drop  of  dilute  ammonia. 

If  the  extract  of  the  acid  is  highly  coloured  it  is  well  to  redissolve  it  in 
a  little  water  and  decolorise  with  animal  charcoal. 


TURKEY-RED    OIL 

This  is  obtained  by  treating  castor  oil  with  sulphuric  acid,  eliminating 
the  excess  of  acid  by  washing  with  water  and  sodium  sulphate  solution  and 
then  neutralising  more  or  less  completely  with  ammonia  or  soda.  It  con- 
sists, therefore,  essentially  of  ammonium  or  sodium  sulpJioricinate.  It  is 
a  clear,  yellow  liquid  with  the  odour  of  castor  oil.  It  dissolves  in  a  small 
quantity  of  water  but  further  addition  of  water  (10  vols.  per  I  vol.  of  the 
oil)  yields  a  perfect,  white  emulsion  which  persists  for  some  hours  and  is 
faintly  acid  to  litmus  paper.  Sulphoricinates  neutralised  with  ammonia 
or  soda  dissolve,  however,  in  water  in  all  proportions,  but  faint  acidification 
of  the  solution  with  a  few  drops  of  acetic  acid  results  in  emulsification.  If 
an  excess  of  acid  or  sodium  chloride  is  added,  either  to  the  emulsion  or 
to  the  solution  of  a  sulphoricinate,  an  oily  layer  separates. 

Sulphoricinates  are  also  completely  dissolved  by  ammonia,  the  solution 
not  being  rendered  turbid  by  dilution  with  water.  Alcohol,  too,  completely 
dissolves  them. 

Ammonium  sulphoricinate  gives  ammonia  when  heated  with  sodium 
hydroxide,  while  sodium  sulphoricinate  is  incinerated  and  the  ash  examined 
for  soda. 

Genuine  Turkey-red  oil  is  sometimes  replaced  by  analogous  preparations 
with  bases  of  sulphonated  olive,  arachis,  cottonseed  or  resin  oil  or  oleic 
acid  and  is  often  adulterated  with  mineral  oil. 

It  is  also  to  be  borne  in  mind  that  certain  emulsive  lubricating  oils. 


448  TURKEY-RED   OIL 

dealt  with  in  the  chapter  on  mineral  oils  (see  p.  368),  have  a  basis  of  sulphori- 
cinate  or  sulpholeate. 

Analysis  of  Turkey-red  oil  comprises  the  following  determinations  and 
tests,  the  second  and  fifth  being  of  special  importance  for  the  evaluation 
of  the  product. 

1.  Solubility    and    Emulsivity. — 2    or    3    c.c.    of    the   oil    and    as 
much  water  should  give  complete  solution  and  addition  of  about  10  vols. 
of  water  should  then  yield  a  persistent  homogeneous  emulsion  of  a  faintly 
acid  reaction. 

Dilute  ammonia  should  also  dissolve  the  oil  completely  and  the  solution 
should  remain  clear  on  dilution  with  a  large  quantity  of  water. 

2.  Total  Fat. — 10  grams  of  the  oil  are  heated  somewhat  in  a  conical 
flask  with  50  c.c.  of  water,  25  c.c.  of  dilute  hydrochloric  acid  (i  :  5)  being 
added  and  the  liquid  boiled  for  3-5  minutes  (until  the  fused  fat  becomes 
clear),  allowed  to  cool,  transferred  to  a  separating  funnel,  into  which  the 
flask  is  washed  with  a  little  water  and  with  200  c.c.  of  ether.     The  whole 
is  vigorously  shaken  and  allowed  to  stand,  the  acid  aqueous  liquid  being 
removed  and  the  ethereal  solution  washed  with  three  successive  quantities 
of  15  c.c.  of  water,  these  wash  waters  being  added  to  the  aqueous  acid  liquor 
and  this  kept  for  the  determination  of  the  sulphuric  acid  (see  3,  below). 
The  bulk  of  the  ether  is  distilled  from  the  ethereal  solution  in  a  conical 
flask  and  the  residue  transferred  to  a  tared  beaker ;    when  the  remainder 
of  the  ether  has  evaporated,  the  residual  mass  is  dried  for  1-2  minutes  over 
a  naked  flame  (a  medium  flame  being  passed  under  the  beaker  until  the 
fat  ceases  to  froth)  and  then  for  half  an  hour  in  an  oven  at  105°  and  weighed. 
The  weight  of  fat  thus  found,  multiplied  by  10,  gives  the  percentage  of 
total  fat  in  the  oil. 

The  fat  may  then  be  used  for  investigating  the  nature  of  the  oil  as  in  5 
(below). 

3.  Determination    of    the    Sulphuric    Acid. — The    aqueous    liquid 
obtained  as  above  is  precipitated  with  barium  chloride,  the  weight  of  barium 
sulphate  thus  precipitated  corresponding  with  the  total  sulphuric  acid  (S03) 
in  the  oil. 

On  the  other  hand  the  sulphuric  acid  as  ammonium  or  sodium  sulphate 
is  determined  by  treating  10  grams  of  the  oil  with  saturated  sodium  chloride 
solution  (quite  free  from  sulphate),  filtering  through  a  moist  filter,  washing 
well  with  the  saturated  sodium  chloride  solution,  diluting  the  filtrate  and 
precipitating  the  sulphate  in  it  with  barium  chloride. 

Subtraction  of  the  percentage  of  S03  as  ammonium  or  sodium  sulphate 
from  the  total  percentage  gives  the  sulphuric  acid  (as  S03)  as  sulphoricinatc 
and  this,  multiplied  by  4*725,  gives  the  percentage  of  sulphoricinoleic  acid 
in  the  oil. 

4.  Neutral  Fat. — 30  grams  of  the  oil  are  dissolved  (in  a  separating 
funnel)  in  50  c.c.  of  water,  20  c.c.  of  ammonia  solution  and  30  c.c.  of  glycerine. 
The  whole  is  shaken  with  two  successive  quantities  of  100  c.c.  of  ether  and 
the  united  ethereal  solutions  washed  several  times  with  water  and  then 
distilled,  the  residue  being  dried  at  100°  and  weighed.     This  weight,  multi- 
plied by  Vo0-,  giyes  tne  percentage  of  neutral  fat  in  the  oil. 


OLEINE   (OLEIC  ACID)  449 

5.  Nature  of  the  Oil. — To  ascertain  if  a  Turkey-red  oil  has  been  pre- 
pared from  castor  oil  or  from  other  oil,  or  adulterated  with  mineral  oil,  the 
total  fat  obtained  by  method  2  (above)  is  examined. 

On  this  fat  the  iodine  and  acetyl  numbers  are  first  determined  :  an 
iodine  number  above  70  and  an  acetyl  number  below  140  show  immediately 
that  the  oil  has  not  been  obtained  from  pure  castor  oil.  The  specific  colour 
reactions  of  the  different  oils  (cottonseed,  sesame,  etc.)  may  then  be  tried. 

It  is  also  to  be  borne  in  mind  that  the  emulsive  oils  prepared  with  olive, 
cottonseed,  colza,  sesame  and  similar  oils  do  not  usually  give  clear  solutions 
with  alcohol,  as  does  pure  emulsive  castor  oil. 

For  detecting  mineral  or  resin  oils  the  saponification  test  is  made. 

6.  Ammonia  or  Soda. — From  7  to  10  grams  of  the  oil  are  dissolved 
in  a  little  ether  and  the  solution  extracted  four  successive  times  with  dilute 
sulphuric  acid  (i  part  of  cone,  acid  and  6  parts  of  water).     The  acid  liquids 
are  then  distilled  with  excess  of  caustic  soda — when  ammonium  sulphori- 
cinate  is  concerned — and  the  ammonia  absorbed  in  standard  acid  ;    with 
sodium  sulphoricinate,  the  acid  liquors  are  evaporated  to  dryness  and  the 
soda  weighed  as  sulphate. 

7.  Iron. — The  oil  is  shaken  with  dilute  sulphuric  acid  and  a  few  drops 
of  potassium  ferrocyanide  solution,  ether  being  then  added  and  the  liquid 
again  shaken  and  then  left  to  stand.     If  iron  is  present,  a  more  or  less  interse 
blue  ring  appears  at  the  zone  of  contact  of  the  two  liquids. 

* 
*  * 

Good  Turkey-red  oils,  prepared  from  castor  oil,  usually  contain  45-60% 
of  total  fatty  substance  (the  rest  being  water),  but  there  are  more  concentrated 
types  with  85-90%  of  fat  (double  oils).  Those  with  about  45%  of  fat  have 
the  specific  gravity  1-017-1-035  at  15°.  The  greater  part  of  the  fat  consists 
of  insoluble  sulpho-acids  and  a  small  part  of  soluble  sulpho-acids  ;  neutral  fat 
is  present  only  in  small  proportion  (1-2%).  No  iron  should  be  present. 

OLEINE 
(Oleic  Acid) 

This  consists  of  the  liquid  fatty  acids  (mainly  oleic  acid) — more  or  less 
completely  separated  from  the  solid  acids— yielded  by  animal  tallow,  bone 
fat,  vegetable  tallow,  palm  oil  and  other  fats.  According  to  its  method  of 
preparation,  it  is  distinguished  as  oleine  oj  saponification  and  distillation 
oleine  (the  latter,  unlike  the  former,  usually  contains  a  large  proportion 
of  hydrocarbons  resulting  from  the  method  of  its  preparation).  In  either 
case  it  is  a  brownish-yellow  or  brownish-red  liquid,  with  a  peculiar  odour, 
easily  soluble  in  85%  alcohol,  acetic  acid  or  petroleum  ether. 

The  most  important  determination  to  be  rrade  in  commercial  oleines 
are  the  following  : 

1.  Acid,  Saponification,  Ester  and  Iodine  Numbers. — These  are 
determined  by  the  ordinary  methods  already  described  in  the  preceding 
chapter.  The  ester  number,  divided  by  2,  gives  the  content  of  neutral  fat. 
The  percentage  of  free  acids  (calculated  as  oleic  acid)  is  usually  called  the 
grade  or  titer  of  the  oleine, 

A.C.  29 


450 


OLEINE   (OLEIC  ACID) 


2.  Unsaponifiable  Substances. — A  preliminary  test  for  these  sub- 
stances is  as  follows  :    6-8  drops  of  the  oleine  and  5  c.c.  of  seminormal 
alcoholic  potash  are  boiled  for  two  minutes  in  a  test-tube  and  then  diluted 
with  15  c.c.  of  water  :  in  this  way  pure  oleine  yields  a  clear  or  almost  imper- 
ceptibly milky  liquid  (distillation  oleine),  whereas  a  turbid  liquid  is  obtained 
with  oleine  mixed  with  mineral  oil. 

To  separate  and  estimate  the  unsaponifiable  substances,  the  methods 
indicated  on  p.  388  are  used. 

To  ascertain  if  the  unsaponifiable  matter  is  composed  of  the  hydro- 
carbons naturally  occurring  in  distillation  oleine  or  of  added  mineral  oil,  the 
rotatory  power  and  the  iodine  number  of  the  unsaponifiable  matter  are 
determined  :  in  the  former  case  the  value  of  [a]D  is  from  +  4-8°  to  +  9-6° 
and  the  iodine  number  62-69,  whereas  mineral  oils  have  practically  no 
rotatory  power  or  iodine  number. 

3.  Determination  of  the  Solid  Fatty  Acids  (Palmitic  and  Stearic). 
— ThL  may  be  effected  by  the  methods  indicated  in  the  preceding  chapter 
(p.  384)  or  by  determining  the  solidifying  point  oj  the  oleine  (see  preceding 
chapter,  p.  418).     From  the  point  of  solidification  obtained,  the  content 
of  stearine  is  deduced  by  means  of  de  Schepper  and  Geitel's  table,  which 
has  been  prepared  with  the  aid  of  mixtures  of  pure  oleine  with  solidifying 
point  5-4°  and  stearine  with  solidifying  point  48°  : 

TABLE    L 
Content  of  Stearine  in  Oleine 


Solidifying 

Percentage  of 

Solidifying 

Percentage  of 

Solidifying 

Percentage  of 

Point 

Stearine 

Point 

Stearine 

Point 

Stearine 

(°C.). 

(48°). 

(°C.). 

(48°). 

(°  C.). 

(48°). 

6 

o-> 

15 

6-6 

23 

157 

7 

0-8 

16 

77 

24 

17-0 

8 

1-2 

17 

8-8 

25 

18-5 

9 

1-7 

18 

9-8 

26 

20  -o 

10 

2-5 

19 

1  1  -2 

27 

21-7 

ii 

3'2 

20 

I2-I 

28 

23-3 

12 

3-8 

21 

I3-2 

29 

25-2 

13 

47 

22 

14-5 

30 

27-2 

14 

5-6 

*** 

A  good  oleine  should  have  an  acid  number  about  179,  corresponding  with 
about  90%  of  free  fatty  acids,  calculated  as  oleic  acid.  Oleines  are  however 
found  with  80-98%  of  free  acids. 

The  content  of  neutral  fat  may  vary  from  o  to  20%  (usually  10-15%). 

The  iodine  number  is  usually  80-90.  If  it  exceeds  90,  the  presence  of  linoleic, 
linolenic  and  other  less  saturated  acids  derived  from  drying  vegetable  oils  is 
indicated. 

The  unsaponifiable  substances  should  not  exceed  2%  in  saponification  oleine, 
but  may  reach  10%  in  distillation  oleine. 

In  saponification  oleine,  up  to  20%  of  neutral  fat  and  up  to  2%  of  unsaponi- 
fiable matter  are  permitted,  and  in  distillation  oleine,  up  to  5%  of  neutral  fat. 


WOOL   FAT   OLEINE— STEARINE  451 

WOOL    FAT    OLEINE 

This  is  the  liquid  part  of  distilled  wool  fat,  consisting  of  free  fatty  acids 
(40-60%),  hydrocarbons  and  a  little  cholesterol  and  isocholesterol. 

It  is  a  more  or  less  turbid  liquid  of  a  reddish-brown  colour  and  more 
or  less  fluorescent  and  with  a  peculiar  odour  recalling  that  of  wool  fat.  It 
is  soluble  in  95%  alcohol,  ether,  benzine,  etc. 

With  cone,  sulphuric  acid,  its  chloroform  solution  gives  a  red  coloration 
with  a  green  fluorescence  (cholesterol).  It  may  be  adulterated  with  mineral 
or  resin  oils  or  resin. 

Its  analysis  includes  the  following  : 

1.  Acid  and  Saponification  Numbers  and  Unsaponifiable  Matter. 
—Use  is  made  of  the  methods  described  in  the  preceding  chapter  (General 
Methods,  7  and  19). 

2.  Mineral  and  Resin  Oils. — From  50  grams  or  more  of  the  oleine 
the  unsaponifiable  substances  are  extracted  by  the  ordinary  methods,  and 
their  specific  gravity,  index  of  refraction,  rotatory  power  (in  about  3-4% 
benzene  solution  and  in  a  tube  10  cm.  long  at  a  temperature  of  18-20°) 
and  iodine  number  determined. 

The  presence  of  mineral  oil  may  be  presumed  when  these  unsaponifiable 
substances  have  very  low  rotatory  power  and  iodine  number.  The  presence 
of  resin  oil  may  be  recognised  by  the  specific  gravity  being  greater  than 
0-917  and  the  refractive  index  above  1-51. 

3.  Resin. — The  soap  solution  remaining  after  the  separation  of  the 
unsaponifiable  matter  is  decomposed  with  an  acid  and  the  fatty  acids  then 
tested  by  means  of  Morawski's  reaction  (see  preceding  chapter :    General 
Methods,  20). 

For  its  quantitative  determination  Twitchell's  method  (ibid.)  is  followed. 

Before  applying  Morawski's  reaction,  it  is  necessary  thoroughly  to  separate 
the  unsaponifiable  matter  in  order  to  remove  the  cholesterol,  which  gives  a 
similar  reaction. 


Pure  wool  fat  oleine  should  not  contain  more  than  60%  of  unsaponifiable 
substances.  These  are  liquid  and  have  approximately  the  appearance  of  mineral 
oils;  they  should,  however,  have:  D  =  0-900-0 -91 7  ;  refractive  index  (at 
18-20°)  =  1-49-1-51  ;  [cf]D  =  -f-  15°  at  least  (in  exceptional  cases  as  low  as 
10°)  and  iodine  number  =  50-80 . 


STEARINE 

(Stearic  Acid) 

This  is  a  mixture  of  solid  fatty  acids  (stearic  and  palmitic) — more  or 
less  completely  separated  from  the  liquid  acids — obtained  from  animal 
tallow  or  from  some  vegetable  fat  and  used  especially  in  the  manufacture 
of  candles. 

According  to  their  methods  of  manufacture,  they  are  distinguished  as 
stearine  of  saponification  and  distillation  stearine,  the  latter  containing, 
unlike  the  former,  iso-oleie  acid  and  stearolactone, 


452  STEARINE   (STEARIC  ACID) 

In  general  stearine  forms  hard,  opaque,  white  masses,  somewhat  greasy 
to  the  feel  and  soluble  in  alcohol,  especially  in  the  hot. 

Analysis  of  commercial  stearines  comprises  principally  the  following  : 

1 .  Solidifying  Point  (Titer) . — This  is  determined  by  Dalican's  method 
(see  p.  418),  the  content  of  stearine  being  deduced  by  means  of  the  corre- 
sponding table  ;    when,   however,   fatty  acids  alone  are    concerned,  the 

number  given  in  the  table  is  multiplied  by  -    -   (see  p.  419). 

95 

2.  Acid,   Saponification   and   Iodine   Numbers.— By  the  methods 
given  in  the  preceding  chapter. 

The  iodine  number  depends  on  the  quantity  of  oleic  acid  (and  maybe 
of  iso-oleic  acid)  in  the  stearine  and  this  may  be  calculated  from  the  iodine 
number  by  means  of  the  formula 

O  =       -  x  I,  or  O  =  i-ii  X  I, 
90, 

where  O  =  oleic  acid  sought    I  =  iodine  number  of  the  stearine  and  90 
is  the  iodine  number  of  pure  oleic  acid. 

3.  Detection     of    Various     Extraneous     Substances. — Commercial 
stearines  sometimes  contain  solid  paraffin  or  ceresine,  wool  fat  stearine,  wax 
and  carnauba  wax.     The  presence  of  such  substances  may  be  suspected  as 
a  rule  when  the  acid  number  of  the  stearine  is  less  than  195,  but  may  be 
proved  definitely  as  follows  : 

(a)  A  few  grams  of  the  stearine  are  digested  in  the  hot  with  95%  alcohol. 
If  the  substance  does  not  dissolve  completely,  the  liquid  is  allowed  to  cool 
and  filtered  and  an  examination  made  of  the  insoluble  part.     The  latter 
may  contain  solid  paraffin  or  ceresine,  beeswax  or  carnauba  wax,  their 
presence  being  indicated  by  the  melting  point,  the  acid  and  saponification 
numbers,  etc.   (sec  articles  on  Paraffin  Wax,  Ceresine  and  Beeswax).1 

(b)  A  quantity  of  the  stearine  is  hydrolysed  with  alcoholic  potash  and  the 
unsaponifiable  substances  extracted  and  examined  by  the  methods  indicated 
on  p.  388  et  seq.  ;   the  presence  of  cholesterol  will  indicate  the  presence  of 
wool  fat  stearine  in  the  substance. 

If  then  it  is  necessary  to  determine  the  various  acids  composing  a  stearine 
(stearic,  palmitic,  oleic)  and  to  test  for  stearolactone,  the  methods  indicated 
in  the  preceding  chapter  (see  pp.  384  and  383)  may  be  followed. 

Finally,  when  the  presence  of  lactones  is  excluded,  that  of  neutral  fat 
may  be  deduced  from  the  ester  number  and  may  be  confirmed  by  testing 
for  glycerine  (see  p.  384). 


Commercial  stearines  usually  solidify  between  48  and  55°  (titer),  the  value 
for  saponification  stearine  being  somewhat  higher  than  that  for  distillation 
stearine . 

The  acid  number  should  not  be  less  than  195 :  if  it  is  less  than  this,  the 
presence  of  neutral  fats  or  extraneous  substances  is  denoted. 

1  The  presence  of  carnauba  wax  may  be  recognised  also  from  the  fact  that,  besides 
lowering  the  acid  and  saponification  numbers  of  the  stearine,  it  raises  the  melting 
point  considerably,  5%  of  carnauba  wax  being  sufficient  to  raise  the  melting  point 
of  a  stearine  by  10°. 


WOOL  FAT  STEARINE  453 

The  saponification  number  is  equal  or  almost  equal  to  the  acid  number  with 
saponified  stearine  and  somewhat  greater  with  distillation  stearine. 

The  iodine  number  is  barely  a  few  units  in  good  saponification  stearines, 
but  may  reach  15-30  in  distillation  stearines,  owing  to  the  presence  of  iso-oleic 
acid. 


WOOL    FAT    STEARINE 

This  is  the  solid  part  of  distilled  wool  fat  and  consists  of  fatty  acids  and 
unsaponifiable  substances  (hydrocarbons,  cholesterol). 

According  to  the  consistency,  it  is  distinguished  as  Saft  stearine,  melting 
below  45°,  and  Hard  stearine  or  Wool  fat  wax,  melting  above  45°. 

In  general,  these  products  have  a  waxy  appearance,  a  yellow  or  brownish 
colour  and  a  pronounced  odour  of  wool  fat,  and  they  are  soluble  in  hot 
alcohol  and  in  ether,  benzene  or  chloroform.  When  treated  with  cone, 
sulphuric  acid,  the  chloroform  solution  turns  red  and  afterwards  violet 
with  a  green  fluorescence  (cholesterol). 

Analysis  of  wool  fat  stearine  includes  determinations  of  the  melting 
point,  acid  number  and  content  of  unsaponifiable  substances,  as  well  as 
tests  for  added  hydrocarbons  (vaseline,  paraffin  wax)  or  resin. 

1.  Vaseline  or  Paraffin  Wax. — The  unsaponifiable  substances  from 
50  grams  of  the  stearine  are  boiled  for  2  hours  in  a  reflux  apparatus  with 
double  their  weight  of  acetic  anhydride.     The  product  is  then  washed 
repeatedly  with  boiling  water  until  the  reaction  is  neutral  and  in  one  part 
the  acetyl  number  is  determined   (see  p.  378).     Another  part   (about  5 
grams)  is  boiled  with  50  c.c.  of  90%  alcohol,  the  liquid  being  filtered  off 
and  the  residue  boiled  with  40  c.c.  and  then  with  30  c.c.  of  90%  alcohol. 
Of  the  part  insoluble  in  alcohol,  which  consists  of  hydrocarbons  alone,  the 
specific  gravity,  rotatory  power  (in  benzene  solution  at  about  20°)  and 
iodine  number  are  determined. 

2.  Resin. — This  is  tested  for  as  in  wool  fat  oleine  (see  p.  451). 


According  to  Marcusson  and  Skopnik  1  and  to  Coen,2  wool  fat  stearines 
may  melt  between  40°  and  65°  ;  they  contain  56-90  %  of  free  acids  (calculated  as 
stearic  acid)  and  9-42%  of  unsaponifiable  substances,  which  are  brown,  fluores- 
cent, pasty  or  semi-liquid  masses  with  a  faint  aromatic  odour  and  have  the 
acetyl  number  about  25-37,  the  [a]D  -f-  12°  to  -(-30°  and  the  iodine  number 

47-74- 

The  portion  of  the  unsaponifiable  matter  which  does  not  combine  with 
acetic  anhydride  (hydrocarbons  free  from  higher  alcohols)  has  0=0-907- 
0-936,  [a]D  =  -f-  12°  to  -(-  21°,  and  iodine  number  =  26-54. 

Addition  of  extraneous  hydrocarbons  may  be  suspected  when  the  acetyl 
number  of  the  unsaponifiable  substances  is  less  than  25  and  the  portion  of  them 
not  combinable  with  acetic  anhydride  has  a  specific  gravity  less  than  0-9,  [a]D 
less  than  -\-  12°  and  an  iodine  number  less  than  26. 

1  Zeitschr.  angew.  Chem.,   1912,  p.  2577. 

2  Annali  del  Lab.  chim.  centrale  delle  Gabelle,  Vol.  VI,  p.  567. 


454  I)£GRAS 

DEGRAS 

Genuine  degras  (natural  degras}  is  a  secondary  product  of  the  chamoising 
of  skins.  It  consists  of  marine  animal  oil  (especially  whale  oil),  in  which 
the  action  of  atmospheric  oxygen  has  led  to  the  formation  of  resinous 
hydroxy-acids  (Degragene),  emulsified  with  water  and  containing  small 
proportions  of  mineral  substances  (soda,  lime,  sulphates)  and  organic 
residues  (hide,  membranous  fragments)  resulting  from  the  method  of 
preparation. 

This  product  forms  a  fairly  dense,  almost  pasty,  yellow  or  orange  liquid, 
which  has  a  special  odour  recalling  that  of  fish  oil  and  remains  homogeneous 
even  on  long  standing. 

Artificial  degras  is  obtained  by  mixing  natural  degras  with  fish,  mineral 
or  resin  oil,  vaseline,  wool  fat,  tallow,  etc.,  or  by  artificial  oxidation  of  fish 
oils,  followed  by  emulsification  with  water  and  sometimes  by  addition  of 
the  other  extraneous  substances  mentioned  above. 

Artificial  degras  is  also  a  yellow  or  orange  dense  liquid,  which  is  usually 
more  liquid  than  the  natural  product  and  has  a  peculiar  fish  oil  odour  ; 
on  long  standing,  it  tends  to  divide  into  two  layers,  the  water  settling  to 
the  bottom. 

Analysis  of  degras  includes  various  determinations  and  tests  to  serve 
as  a  guide  in  ascertaining  if  it  is  a  natural  or  artificial  product,  if  it  is  pure, 
that  is,  based  solely  on  fish  oils,  or  if  it  is  mixed  with  tallow,  wool  fat,  mineral 
oils,  vaseline  or  resin  oils,  these  being  the  most  frequent  additions  to 
degras. 

The  principal  determinations  are  as  follows  : 

1.  Water . — 10  grams  of  the  degras  are    placed  in  a  porcelain  dish 
previously  heated  to  redness  with  about  10  grams  of  coarse  quartz  sand 
and  tared  ;   the  fat  is  mixed  well  with  the  sand  and  the  dish  and  contents 
dried  at  120°  until  of  constant  weight   (4-5  hours).     The  loss  in  weight 
gives  the  water. 

2.  Non-fatty  Substances   (Organic  Residues). — 20  grams    of  the 
degras    are  dried    in  an  oven  at  120°  or  even  over  a  direct  flame,  the 
liquid  being  stirred  with  a  thermometer  and  care  taken  that  its  temperature 
does  not  exceed  105°  ;   the  dried  product  is  dissolved  in  petroleum  ether 
and  the  solution  filtered  through  a  tared  filter,  the  insoluble  mattei  being 
washed  with  petroleum  ether  and  then  with  a  little  ether  or  benzene  and 
alcohol,  dried  at  100°  and  weighed. 

This  insoluble  matter  consists  principally  of  epidermis  and  hide  residues 
readily  recognisable  with  a  lens  or  microscope,  together  with  a  few  other 
impurities. 

On  the  other  hand,  evaporation  of  the  petroleum  solution  and  weighing 
of  the  residue  dried  at  105°  gives  the  total  fat  ;  the  latter  is  used  for  the 
determinations  indicated  under  4  (below). 

3.  Ash.— 10  grams  of  the   degras  are  carefully   heated  in  a  platinum 
dish  over  a  naked  flame  until  copious  fumes  are  emitted,  the  dish  being 
then  heated  more  strongly  on  a  sand-bath  and  finally  in  a  muffle  at  a  dull 
red  heat.     The  ash  is  mainly  alkali  and  alkaline-earthy  sulphates  ;    it  is 


DfiGRAS  455 

well  to  test  it  for  oxide  of  iron,  which  should  be  present  barely  in  traces, 
since  degras  containing  iron  spots  the  leather. 

4.  Acid   and    Saponification    Numbers. — These  are  determined  in 
the  usual  way  on  the  dry  fat  from  the  determination  of  the  non-fatty  sub- 
stances (2).     From  the  acid  number  the  percentage  of  free  acids  expressed 
as  oleic  acid  (see  p.  374)  is  calculated. 

5.  Degragene. — This  is  the  special  resinous  substance  formed  by  the 
oxidation  of  the  fish  or  blubber  oils  x  and  is  what  gives  body  to  the  degras, 
increases  its  power  of  emulsivity  with  water  and  renders  it  specially  adapted 
to  the  treatment  of  skins.     It  is  determined  as  follows  2 : 

10  grams  of  the  degras,  either  as  it  stands  or  after  drying  at  100°  as 
indicated  under  2  (above),  are  dissolved  together  with  7  grams  of  caustic 
soda  in  10  c.c.  of  water  and  50  c.c.  of  alcohol,  the  solution  being  heated  on 
a  water-bath  in  a  reflux  apparatus  until  saponification  is  complete  (about 
2  hours).  The  alcohol  is  then  expelled,  the  soap  dissolved  in  water  and 
acidified  with  hydrochloric  acid,  and  the  whole  boiled  until  the  mixture  of 
fatty  acids  and  degragene  becomes  quite  fluid.  When  cool,  the  mass  is 
transferred  to  a  separating  funnel  and  the  flask  rinsed  out  with  about  150 
c.c.  of  petroleum  ether  boiling  below  75°  ;  the  whole  is  well  shaken  and 
allowed  to  stand  until  the  aqueous  acid  liquid  separates  sharply  from  the 
petroleum  solution,  the  former  being  then  run  off.  The  funnel  then  con- 
tains the  petroleum  ether  solution  of  the  fatty  acids  and  of  the  unsaponifiable 
substances  of  the  degras,  together  with  an  insoluble,  blackish,  resinous 
solid  constituting  the  degragene,  which  adheres  well  to  the  walls  of  the 
funnel,  so  that  the  petroleum  solution  may  be  poured  from  the  top  of  the 
funnel  without  any  of  the  degragene  being  lost.  The  degragene  is  then 
washed  with  a  little  petroleum  ether  and  dissolved  in  hot  alcohol,  the  solu- 
tion being  filtered  if  necessary,  the  alcohol  evaporated  and  the  residue 
dried  at  100-105°  and  weighed. 

6.  Unsaponifiable  Substances. — According  to  Baldracco,3  these 
may  be  determined  exactly  as  follows  :  15-20  grams  of  the  degras  are 
saponified  by  boiling  with  5  grams  of  caustic  potash  dissolved  in  10  c.c. 
of  water  and  50  c.c.  of  alcohol  for  2-2|  hours  in  a  reflux  apparatus,  the 
liquid  being  then  transferred  to  a  dish  and  the  alcohol  completely  expelled 
by  evaporation  on  a  water-bath.  The  residue  is  well  mixed  with  8  grams 
of  sodium  bicarbonate  and  50-60  grams  of  coarse  quartz  sand  previously 
washed  and  calcined,  and  completely  dried  in  an  oven  at  110°.  The  mass 
is  then  broken  into  small  pieces,  placed  in  an  extraction  thimble  and  ex- 
tracted with  petroleum  ether  boiling  below  75°. 

The  petroleum  solution  is  washed  several  times  with  water  in  a  separating 
funnel  and  then  evaporated,  the  residue,  when  dried  at  110°  and  weighed, 

representing  the  unsaponifiable  matter  contained  in  the  degras. 
» 

1  The  largest  proportions  of  degragene  are  furnished  by  whale  oil  and  cod-liver  oil, 
which  yield,  therefore,  the  best  degras. 

a  This  is  the  method  proposed  by  the  Committee  for  the  analysis  of  degras  at  the 
Seventh  Congress  of  the  International  Association  of  Leather  Trade  Chemists,  Turin, 
1904. 

The  other  determinations  are  also  those  suggested  by  this  Committee. 

3  See  preceding  note. 


456  CANDLES 

This  residue  may  then  be  tested  for  cholesterol  and  for  mineral  and 
resin  oils  in  the  way  indicated  on  p.  388,  in  order  to  ascertain  if  the  degras 
contains  wool  fat,  mineral  oils  and  other  unsaponifiable  matters. 


Good  degras  is  golden-yellow  or  orange  and  homogeneous  and  keeps  well. 

Natural  degras  usually  contains  15-25%  of  water,  while  the  artificial  pro- 
ducts contain  10-25%. 

The  other  components  may  vary  within  the  following  limits,  which  are 
referred  to  the  dry  degras  (free  from  water)  : 

The  non-fats  (various  organic  residues)  may  reach  8%  in  natural  degras 
(ordinarily  2-5%),  but  are  less  than  i%  in  artificial  degras. 

The  ash  may  amount  to  5%  with  natural  degras,  but  is  less  than  i%  in 
the  artificial  product  ;  it  should  contain  only  traces  of  iron  (not  more  than 
0-05%  of  the  original  degras). 

The  free  fatty  acids,  calculated  as  oleic  acid,  may  vary  from  20  to  30%  in 
natural  degras,  but  are  usually  less  than  20%  in  the  artificial  ones. 

The  saponification  number  is  above  200  (220-240)  in  natural  degras  and 
not  less  than  190  in  artificial  degras.  A  value  less  than  190  (referred  to  the 
dry  substance)  denotes  the  presence  of  extraneous  matter,  such  as  mineral  or 
resin  oils,  vaseline  or  wool  fat. 

The  proportion  of  degragdne  is  somewhat  variable,  since  it  depends  on  the 
mode  of  preparation  of  the  degras.  Usually  natural  degras  contains  6-20% 
and  the  artificial  product  not  more  than  10%  of  degragene. 

The  unsaponifiable  matter  does  not  exceed  3%  in  pure  degras,  whether  natural 
or  artificial,  but  is  considerably  higher  in  products  adulterated  with  mineral 
or  resin  oils,  vaseline  or  wool  fat. 

CANDLES 

Three  types  of  candles  are  usually  sold  :    stearine,  paraffin  and  wax. 

Stearine  candles,  which  are  opaque  and  white,  should  be  made  from 
stearine  (mixture  of  stearic  and  palmitic  acids,  etc.  ;  see  Stearine),  but 
very  often  they  contain  a  certain  quantity  of  paraffin  wax  (up  to  50%) 
and  sometimes  ceresine  or  a  small  quantity  of  carnauba  wax  (to  raise  the 
melting  point). 

Paraffin  candles,  which  are  translucent  and  white,  are  made  from  paraffin 
wax  with  a  high  melting  point  (about  50°),  usually  with  the  addition  of 
3-15%  or  even  more  (up  to  about  33%)  of  stearine,  such  being  mixed  or 
composite  candles. 

Wax  candles,  which  are  yellowish  and  opaque  and  possess  the  charac- 
teristic odour  of  wax,  should  be  made  from  pure  beeswax,  but  they  are 
nowadays  usually  made  from  mixtures  of  wax,  paraffin  wax,  ceresine  and 
stearine,  the  wax  being  present  often  in  small  amount. 

Analysis  of  candles  is  usually  made  with  the  object  of  determining  the 
composition,  but  includes  also  tests  of  the  illuminating  power  and  bending 
properties. 

1.  Composition. — An  idea  of  this  is  obtained  firstly  from  the  objective 
characters  (see  above).  The  composition  is  then  determined  qualitatively 
and  quantitatively  by  determinations  of  the  solidifying  point,  of  the  acid, 
saponification  and  iodine  numbers,  of  the  unsaponifiable  substances  and 
the  nature  of  the  latter,  the  instructions  laid  down  in  the  articles  on  stearine, 


CANDLES  457 

paraffin  wax,  ceresine  and  beeswax  being  followed  according  to  the  type 
of  candle  examined. 

For  the  quantitative  determinations  it  is  well  to  melt  a  whole  candle 
or  at  least  various  pieces  taken  from  several  candles  at  different  points  in 
order  to  obtain  a  homogeneous  and  representative  sample. 

It  is  further  necessary  to  determine  the  weight  of  the  wick,  several 
pieces  being  broken  from  one  or  more  candles  and  weighed  and  the  wick 
then  carefully  separated  and  weighed  :  the  weight  of  the  wick  is  referred 
to  loo  parts  of  candle. 

The  commonest  cases  of  analysis  of  candles  are  the  following  : 

(a)  MIXED  STEARINE  AND  PARAFFIN  (OR  CERESINE)  CANDLES.    About 
10  grams  of  the  sample  are  heated  and  shaken  with  50  c.c.  of  90%  alcohol 
on  the  water-bath,  the  liquid  being  subsequently  titrated  with  decinormal 
potassium  hydroxide  in  presence  of  phenolphthalein  :    I  c.c.  N/io-KOH  = 
0-027  gram  of  stearine  (mean  molecular  weight  of  ordinary  stearine  =  270). 

The  liquid  is  then  again  heated  on  the  water-bath  for  about  an  hour, 
with  frequent  shaking,  with  4-5  c.c.  of  concentrated  potassium  hydroxide 
solution  to  saponify  the  small  quantity  of  neutral  fat  or  any  lactones  present 
in  the  stearine  (for  greater  precision  the  saponification  number  also  may 
be  determined).  The  solution  is  then  diluted  with  water  and  allowed  to 
cool  until  the  paraffin  is  thoroughly  solidified  to  a  solid  disc,  the  aqueous 
liquid  being  then  decanted  off  and  the  paraffin  washed  several  times  with 
water,  being  heated  and  cooled  each  time.  The  washed  paraffin  is  finally 
collected  into  a  dish,  dried  in  an  oven  at  105°  and  weighed. 

The  paraffin  thus  separated  is  then  tested  for  ceresine  by  the  methods 
given  on  p.  364. 

The  stearic  acid  (stearine)  calculated  from  the  acid  number  and  the 
paraffin  weighed  directly  are  then  referred  to  100  parts  of  candle,  allowance 
being  made  for  the  weight  of  the  wick  \see  example  given  below  for  case  b). 

For  rapid,  approximate  determinations  it  is  sufficient  to  calculate  the 
stearic  acid  from  the  acid  number  and  the  paraffin  by  difference. 

(b)  MIXED  WAX,  STEARINE  AND  PARAFFIN  CANDLES.     In  these  candles 
it  may  be  necessary  to  calculate  either  all  three  of  the  components  or  only 
the  paraffin  (or  ceresine). 

i.  Determination  of  all  of  the  components.  The  acid  and  saponification 
numbers  are  determined  in  the  usual  way,  the  various  components  being 
then  calculated  as  in  the  following  example. 

EXAMPLE  :  The  wick  of  a  candle  is  found  to  represent  o  -4  %  of  the  weight 
of  the  candle,  while  the  wick-free  mass  has  : 

Acid  number  =  77-0 
(%)     Sa^ojuficatiQn___-     ,,      =  84-7, 
so  that 

••>.  Kster  number          77. 

Assuming  the  mean  ester  number  of  wax  to  be  75,  the  mean  saponification 
number  of  wax  to  be  95  and  the  mean  saponification  number  of  stearic  acid 
to  be  207,  the  various  components  are  calculated  as  follows  : 
(a)  The  wax  (x)  is  given  by  the  ester  number, 

75  :  100  :  :  7-7  :  it, 
consequently, 

X  =  JO -^6%    of    -u'it.V. 


458  SOAPS 

(b)  The  saponification  number  (y)  due  to  the  wax  will  be  given  by 

TOO  :  95  =  10-26  :  y, 
so  that 

y  =  9-75- 

This  number  y  is  deducted  from  the  saponification  number  found  for  the  sub- 
stance, 

847-975  =  74-95. 
and  from  this  the  stearic  acid   (z)  is  deduced  from  the  proportion, 

207  :  100  =  74-95  :  z, 
so  that, 

z  =  36-11%  of  stearic  acid. 

(c)  The  solid  paraffin  is  then  given  by  difference, 

100  —  (10-26  4-  36-11)  =  53-63%  of  paraffin. 

(d)  The  composition  of  the  entire  candle   (with  the  wick)  is  thus  : 

Wick 0-40% 

Wax  .........      10-22 

Stearic  acid          .......      35-96 

Paraffin       .          .          .          .          .          .          .          .53-42 

2.  Determination  of  the  paraffin  (or  ceresine)  alone.  In  this  case  10  grams 
of  the  candle  are  boiled  for  3-4  hours  with  alcoholic  potash  in  a  flask  fitted 
with  a  long  tube  to  act  as  reflux  condenser  and  then  left  to  cool  until  the 
paraffin  has  set  well  at  the  suiface  of  the  liquid.  The  latter  is  then  poured 
off  together  with  all  the  unsaponifiable  matters  of  the  wax  which  remain 
suspended  in  a  flocculent  form,  care  being  taken  that  the  whole  of  the 
paraffin  remains  in  the  flask.  The  paraffin  is  then  again  boiled  for  an  hour 
with  alcoholic  potash,  the  whole  being  afterwards  transferred  while  still 
hot  to  a  separating  funnel,  the  flask  being  rinsed  out  with  boiling  water 
so  as  to  obtain  all  the  paraffin  in  the  funnel.  The  aqueous  alcoholic  liquid 
is  run  away  and  the  paraffin  remaining  in  the  funnel  washed  several  times 
with  hot  water  and  subsequently  rinsed  out  into  a  small  beaker  with  the 
help  of  very  hot  water.  After  cooling,  the  solid  paraffin  disc  is  dried  at 
100-105°  in  a  tared  dish  and  weighed. 

This  paraffin  is  then  tested  for  ceresine  by  the  methods  given  under 
Paraffin  wax  and  Ceresine. 

2.  Illuminating   Power.- — This  is  measured  as  with  petroleum   (see 
Chapter  VIII,  Lighting  Oil,  7). 

3.  Bending  Test.— This  test,  made  especially  with  paraffin  candles, 
consists  in  introducing  the  base  of  the  candle  into  a  suitable  support  so  that 
the  candle  is  horizontal  and  leaving  it  in  a  room  at  a  constant  temperature 
of  22-25°  f°r  some  hours  to  ascertain  if  it  becomes  curved  and,  if  so,  to 
what  extent.     A  standard  candle  is  used  for  purposes  of  comparison. 


SOAPS 

Soaps  consist  essentially  of  potassium  or  sodium  salts  of  fatty  acids, 
potash  soaps  being  soft  and  the  more  common  soda  soaps  hard. 

Besides  these  salts,  all  soaps  contain  water  and,  according  to  their 
method  of  manufacture  and  use  :  free  alkali  (hydroxides  or  carbonates), 
neutral  fat,  colophony  (as  alkali  resinates),  and  various  extraneous  sub- 


SOAPS  459 

stances  such  as  alkali  carbonates,  chlorides,  sulphates,  silicates  and  borates, 
kaolin,  talc,  starch,  sugars,  glycerine,  alcohol,  etc.,  essential  oils  (in  scented 
soaps)  or  antiseptic  and  medicinal  substances  (in  medicinal  soaps). 

The  purest  soaps  are  the  so-called  curd  soaps,  obtained  by  precipitation 
with  common  salt,  and  those  prepared  from  the  free  fatty  acids.  Such 
soaps  are  neutral  or  only  slightly  alkaline,  and  this  group  includes,  for 
instance,  toilet  soaps  in  general,  so-called  Marseilles  white  soap  and  certain 
mottled  soaps. 

So-called  "  cold  "  soaps,  obtained  by  saponifying  fats  with  an  alkaline 
lye  without  adding  common  salt,  are  usually  very  alkaline  ;  they  contain 
the  glycerine  and  all  the  impurities  of  the  fats  and  alkali  used.  Potash 
soaps  belong  to  this  class. 

Soaps  are  analysed  to  ascertain  their  composition  and  to  see  if  they 
are  suited  to  definite  uses.  Analysis  includes  mainly  determinations  of 
the  water,  total  fat,  alkali,  resin,  glycerine,  etc. 

1.  Sampling. — The  various  determinations  require  at  least  100  grams 
of  soap,  which  is  stored  in  a  well-dried  and  closed  glass  jar. 

With  soap  in  small  pieces  or  cakes,  these  are  cut  into  at  least  four  parts 
(lengthwise  and  crosswise),  from  which  thin  shavings  are  taken  and  cut 
up  finely,  the  whole  being  thoroughly  mixed  and  a  portion  taken  for  analysis. 

With  soap  in  blocks  or  large  rectangular  pieces,  two  triangular  prisms 
with  their  bases  on  two  opposite  sides  are  taken  so  as  to  represent  propor- 
tionately the  dried  outer  part  and  the  more  hydrated  inner  part  ;  these 
prisms  are  rapidly  cut  up,  well  mixed  and  the  sample  to  be  analysed  then 
taken. 

Soft  or  powdered  soaps  are  well  mixed  with  a  spatula  or  in  a  mortar  and 
the  sample  then  taken. 

2.  Water.— In  a  platinum  dish,  tared  with  a  glass  rod,  5-8  grams  of 
the  soap  are  weighed,  the  dish  being  then  heated  in  an  oven  first  at  60-70° 
and  then  at  ioo-io56  until  of  constant  weight,  the  mass  being  stirred  from 
time  to  time  with  the  rod.     Loss  of  weight  represents  water. 

For  soft  soaps  or  others  containing  a  large  proportion  of  water,  a  certain 
amount  of  siliceous  sand  or  ground  pumice,  previously  ignited,  is  tared 
in  the  dish  with  the  glass  rod.1 

3.  Total    Fat. — 20    grams    of    the    soap,    dissolved    in    water,    are 
decomposed  by  excess  of  dilute  sulphuric  acid  (i  :  3)  or  of  normal  sulphuric 
acid  (see  also  4),  the  solution  shaken  with  100  c.c.  of  petroleum  ether,  b.pt. 
not  above  65°,  and  the  acid  liquid  separated  and  again  shaken  with  100 
c.c.  of  petroleum  ether.     The  two  petroleum  extracts  are  united,  washed 
with  water,  filtered  (if  necessary)  into  a  tared  dish  and  evaporated  at  a 
low  temperature,  the  residue  being  dried  in  an  oven  at  about  110°  to  constant 
weight. 

This  gives  the  total  fat,  which,  besides  the  fatty  acids  and  resin  acids 
constituting  normal  soap,  may  contain  also  neutral  fat  and  unsaponifiable 
substances  ;  it  is  therefore  examined  further  (see  below:  5,  8  and  n). 

1  If  the  soap  contains  alcohol,  hydrocarbons  or  other  volatile  substances,  these 
are  vaporised  with  the  water  ;  in  such  cases  the  water  is  determined  by  difference 
after  the  other  components  of  the  soap  have  been  determined. 


46o  SOAPS 

The  aqueous  acid  liquid,  separated  from  the  petroleum  ether,  may  be 
utilised  for  the  determination  of  the  alkalies  (see  4). 

4.  Total  Alkalies. — This  determination  may  be  combined  with  the 
preceding  one  of  the  total  fat.     For  this  purpose  it  is  sufficient  to  decompose 
the  aqueous  solution  of  20  grams  of  the  soap  with  100  c.c.of  normal  sulphuric 
acid  and  then  to  proceed  as  in  3,  care  being  taken  to  lose  no  trace  of  the 
aqueous  acid  liquid  separated  from  the  petroleum  ether  solution. 

This  liquid,  collected  quantitatively  in  a  conical  flask,  is  titrated  with 
normal  potassium  hydroxide  solution  in  presence  of  methyl  orange. 

The  difference  between  the  volume  of  normal  acid  added  to  the  soap 
solution  and  the  volume  of  normal  alkali  necessary  to  neutralise  the  remain- 
ing free  acid,  represents  the  total  alkali — existing  as  hydroxides,  carbonates, 
silicates,  borates  and  soaps — in  the  soap.  This  is  expressed  as  sodium 
oxide  for  hard  or  powdered  soap,  and  as  potassium  oxide  for  soft  soap  ; 
i  c.c.  normal  H2SO4  =  0-031  gram  of  Na2O  =  0-047  gram  of  K2O. 

5.  Alkalies   combined   with  Fatty   Acids.— The  alkalies  combined 
with  fatty  (or  resin)  acids,  that  is,  as  soaps,  are  deduced  from  the  acid 
number  of  the  total  fat  obtained  as  in  3. 

The  acid  number  is  determined  as  on  p.  374,  and  the  results  are  expressed 
as  Na2O  for  hard  or  powdered  soap  and  as  K2O  for  soft  soap. 

6.  Free  Alkalies, —  The  presence  of  excess  of  alkali  in  a  soap  is  detected 
(i)  by  dissolving  I  part  of  the  soap  in  50  parts  of  95%  alcohol  and  adding 
a  few  drops  of  phenolphthalein  solution  (red  coloration),  or  (2)  by  dropping 
on  to  a  section  of  the  soap,  recently  cut,  a  drop  of  mercuric  chloride  solution 
(yellow  coloration)  or  mercurous  nitrate  solution  (black  coloration). 

Quantitatively  free  alkalies  as  hydroxide  and  as  carbonate  are  deter- 
mined as  follows  : 

(a)  ALKALIES  AS  HYDROXIDE.     A  solution  of  10-15  grams  of  anhydrous 
glycerine  in  100  c.c.  of  absolute  alcohol  is  neutralised,  if  necessary,  with  a 
few  drops  of  alcoholic  potash    (phenolphthalein  as  indicator).     5   grams 
of  the  soap  are  then  dissolved  in  it  and  2-5  c.c.  of  cold,  saturated  alcoholic 
strontium  chloride  solution  added  to  precipitate  the  alkali  carbonates,  the 
free  alkalinity  being  then  titrated  with  standard  alcoholic  stearic  acid  solu- 
tion in  presence  of  phenolphthalein.1 

(b)  ALKALIES  AS  CARBONATE.     If  the  soap  does  not  contain  silicates, 
borates  or  other  alkaline  salts,  the  alkalies  as  carbonate  may  be  calculated 
indirectly  or  by  difference,  by  subtracting  from  the  total  alkali  (see  4)  the 
sum  of  the  alkali  as  hydroxides  and  that  combined  with  the  fatty  acids 
(see  5   and  60),  all  expressed  as  Na2O  or  K2O  :  this  difference,  converted 
into  Na2C03  or  K2CO3,  represents  alkalies  as  carbonates. 

When  silicates,  borates  or  other  alkaline  salts  are  present,  the  best  way 
to  determine  the  carbonates  is  to  decompose  the  soap  with  dilute  sulphuric 


1  The  alcoholic  stearic  acid  solution  is  prepared  by  dissolving  about  7  grams  of 
stearic  acid  in  a  litre  of  absolute  alcohol  (approximately  N/4O  solution)  and  the  titer, 
i.e.,  the  number  of  grams  of  NaOH  or  KOH  corresponding  with  i  c.c.,  determined  by 
N/io-potassium  hydroxide  solution  in  presence  of  phenolphthalein.  With  reference 
to  this  and  other  determinations,  see  the  paper  by  G.  Gianoli,  "  On  Uniform  Methods 
of  Soap  Analysis"  (L'lndustria,  1914,  p. 


SOAPS  461 

acid  and  absorb  the  carbon  dioxide  liberated  in  caustic  potash  solution  in 
the  ordinary  manner.1 

7.  Free  Fatty  Acids.— These  are  determined  only  when  the  soap  does 
not  exhibit  an  alkaline  reaction. 

20  grams  of  the  soap  are  dissolved  in  neutral  60%  alcohol  and  the 
solution  titrated  with  alcoholic  decinormal  caustic  potash  in  presence  of 
phenolphthalein.  The  acidity  is  expressed  as  oleic  acid  :  i  c.c.  N/io-KOH 
=  0-0282  gram  of  oleic  acid. 

8.  Neutral   Fat   and   Unsaponifiable   Substances. — From  6  to   8 
grams  of  the  total  fat,  extracted  as  in  3,  are  dissolved  in  about  .50  c.c.  of 
96%  alcohol  and  the  liquid  neutralised  with  seminormal  alcoholic  caustic 
potash  in  presence  of  phenolphthalein  (to  a  faint  pink  coloration)  ;   it  is 
then  diluted  with  about  50  c.c.  of  water  and  extracted  successively  with 
100  c.c.,  50  c.c.,  and  50  c.c.  of  petroleum  ether  (b.pt.  not  above  65°).     The 
united  petroleum  ether  solutions  are  washed  three  times  with  three  quantities 
of  10-20  c.c.  of  58%  alcohol  and  then  evaporated,  the  residue  being  dried 
at  100-105°  and  weighed. 

This  gives  the  neutral  fat  plus  any  unsaponifiable  substances  contained 
in  the  soap. 

In  presence  of  the  latter  (which  may  be  detected  by  a  separate  test),, 
the  weighed  residue  must  be  saponified  with  alcoholic  potash,  the  solution 
extracted  with  petroleum  ether  in  the  manner  described  above,  and  the 
new  extract,  representing  the  unsaponifiable  substances,  weighed.  The 
neutral  fat  is  then  given  by  difference. 

9.  Resin. — The  presence  of  resin    (colophony)   in  a  soap  is  readily 
detected  by  the  application  of  Morawski's  reaction  (see  p.  390)  to  the  fatty 
acids  obtained  from  the  soap  itself,  provided  the  latter  does  not  contain 
wool  fat,  in  which  case  the  test  is  made  on  the  fatty  acids  after  elimination 
of  the  unsaponifiable  matter. 

The  quantitative  determination  of  the  resin  is  effected  by  Twitchell's 
method  (see  p.  390) 

10.  Glycerine. — This  occurs  in  "cold"  soaps  and  in  soft  or  potash 
soaps  (3-5%),  in  which  its  presence  is  due  to  the  method  of  preparation, 
and  also  in  transparent  or  glycerine  soaps,  to  which  it  is  purposely  added. 

For  its  determination,  20-25  grams  of  the  soap  are  dissolved  in  hot 
water,  decomposed  by  means  of  dilute  sulphuric  acid  and  filtered  to  remove 
the  fatty  acids.  The  filtrate  is  neutralised,  defecated  vwith  lead  acetate, 
made  up  to  a  definite  volume  and  filtered,  the  glycerine  being  estimated  in 
an  aliquot  part  by  the  dichromate  method  (see  Glycerine). 

If  the  soap  contains  ethereal  oils,  sugar,  dextrin  or  other  substance 
oxidisable  by  dichromate,  this  method  is  inapplicable.  In  such  cases  the 
defecated  aqueous  liquid  is  evaporated  with  addition  of  lime  and  the  glycerine 
then  extracted  with  alcohol  and  ether  in  the  manner  described  for  the 
determination  of  glycerine  in  wine. 

11.  Nature  of  the  Constituent  Fats. — The  external  characters  of 
soaps  give  some  indication  of  the  nature  of  the  fatty  matters  used  in  the 
manufacture.     White  and  mottled  soaps  are  mostly  prepared  from  tallow 

*  See  last  part  of  preceding  foot-note. 


462  SOAPS 

and  olive,  arachis,  sesame,  cottonseed  and  coco-nut  oils  ;  yellow  soaps 
may  contain  resin  and  palm  oil,  and  green  or  brown  ones,  sulphocarbon 
oil  and  resin.  Further,  the  solidifying  point,  acid  and  iodine  numbers 
and  certain  colour  reactions  and  other  investigations  of  the  fatty  acids 
obtained  from  a  soap  give  information,  up  to  a  certain  point,  of  the  char- 
acter of  the  fats  used. 

For  example  :  Soaps  prepared  from  oleine  give  fatty  acids  which  solidify 
at  a  low  temperature  and  contain  only  small  quantities  of  solid  acids  (for 
examination  of  these,  see  p.  384). 

Soaps  from  coco-nut  oil  give  fatty  acids  with  an  acid  number  above  205 
and  a  low  iodine  number. 

Those  from  linseed  and  other  drying  oils  contain  hydroxy- acids  insoluble 
in  the  cold  in  petroleum  ether  and  yield  fatty  acids  with  a  high  iodine 
number. 

Soaps  from  cottonseed,  sesame  and  arachis  oils  give  fatty  acids  which 
show.Milliau's  and  Villavecchia  and  Fabris'  reactions  and  contain  arachidic 
acid  (see  Cottonseed,  Sesame  and  Arachis  Oils,  preceding  chapter). 

Resin  soaps  give  the  reaction  for  resin  with  acetic  anhydride  and  sul- 
phuric acid  (see  9). 

Tests  for  cholesterol  and  phytosterol  (see  Hog's  Fat)  show  whether  a 
soap  contains  animal  or  vegetable  fats. 

12.  Extraneous  Substances.— These  may  be  of  varied  character 
and  principally  as  follows  : 

(a)  MINERAL  SUBSTANCES.     Alkaline  chlorides,   sulphates,   carbonates 
and  phosphates,  water  glass,  borax,  heavy  spar,  kaolin,  talc,  siliceous  sand, 
pumice,  tiipoli,  etc.     Some  soaps  (especially  powdered)  contain  also  oxidising 
agents,  such  as  sodium  peroxide,  perborates,  percarbonates  and  persulphates. 

All  these  substances  may  be  recognised  and  determined  by  treating 
the  soap  with  absolute  alcohol  and  examining  the  insoluble  residue  by  the 
ordinary  analytical  methods,  both  qualitative  and  quantitative. 

(b)  VARIOUS  ORGANIC  SUBSTANCES.    These  may  consist  of  starch,  flour, 
dextrin,  sugars   (saccharose,  glucose,  molasses),  vegetable  gum,  albumin 
and  casein.     Such  substances  also  remain  undissolved  when  the  soap  is 
treated  with  absolute  alcohol  and  may  be  detected  in  the  residue  by  means 
of  the  microscope,  by  treating  with  iodine  (starch,  dextrin),  by  the  rotatory 
and  reducing  powers  (sugars),  by  the  way  in  which  they  burn  (proteins, 
etc.). 

(c)  ALCOHOL.     About  50  grams  of  the  soap  are  dissolved  in  100  c.c.  of 
tepid  water  and  decomposed  with  a  slight  excess  of  dilute  sulphuric  acid 
and  filtered.     The  filtrate  (which  should  not  be  much  more  than  150  c.c.)  is 
neutralised  with  potash  and  distilled,  100  c.c.  of  distillate  being  collected. 
From  the  density  of  this  the  alcohol  is  calculated. 

(d)  PERFUMES.     These  consist  of  various  essential  oils  or  of  nitrobenzene 
(mirbane  oil).     To  detect  them,  30-50  grams  of  the  soap  are  dissolved  in 
a  little  water,  decomposed  with  a  slight  excess  of  dilute  sulphuric  acid  and 
distilled  in  a  current  of  steam,  the  distillate  being  collected  in  a  very  narrow 
cylinder, 

The  volatile  oil  collects  in  drops  or  in  a  thin  layer  at  the  surface  of  the 


GLYCERINE  463 

distilled  water.  Ether  is  then  added  and  the  whole  transferred  to  a  small 
separating  funnel,  the  cylinder  being  rinsed  out  with  ether.  After  shaking, 
the  water  is  withdrawn  and  the  ethereal  solution  allowed  to  evaporate  at  the 
ordinary  temperature  in  a  small  dish  ;  this  yields  the  volatile  oil,  which  may 
be  identified  by  its  odour  and,  if  in  sufficient  quantity,  by  other  characters 
To  identify  nitrobenzene,  the  ethereal  extract  obtained  in  the  above 
manner  is  dissolved  in  a  little  alcohol  and  a  scrap  of  zinc  and  2-3  c.c.  of 
dilute  sulphuric  acid  added  to  the  solution.  After  2-3  hours  the  liquid  is 
filtered  into  a  dish  and  the  filtrate  exposed  for  an  instant  to  chlorine  issuing 
from  a  test-tube  containing  a  little  potassium  chlorate  and  cone,  hydro- 
chloric acid  :  a  persistent  violet  coloration  is  produced  (Armani  and  Barboni). 

Soaps  based  on  coco-nut  or  palm  oil  give,  with  steam,  a  small  quantity  of 
volatile  acids  of  peculiar  odour,  which  must  not  be  confused  with  that  of  soap 
containing  added  perfume. 

(e)  MEDICINAL  SUBSTANCES.  Medicinal  soaps  are  made  with  the  most 
varied  substances,  mostly  antiseptics,  among  which  are  formalin,  phenol, 
naphthalene,  tar,  ichthyol,  camphor,  sulphur,  salicylic  and  boric  acids, 
mercury  salts,  arsenical  compounds,  juices  of  medicinal  herbs,  etc. 

These  may  be  tested  for  by  shaking  the  soap  with  ether,  evaporating 
the  ethereal  solution  and  examining  the  residue  by  suitable  methods,  or 
by  dissolving  the  soap  in  water,  precipitating  with  barium  chloride  and 
washing  the  barium  soap  thus  formed  with  alcohol  or  ether. 

Mercury  and  arsenic  compounds,  boric  acid  and  the  like  may  be  detected 
by  decomposing  the  soap  with  hydrochloric  or  nitric  acid  and  then  testing 
the  acid  aqueous  liquid. 

One  of  the  commonest  medicinal  soaps  contains  carbolic  acid.  To 
determine  the  proportion  of  the  phenol,  5-10  grams  of  the  soap  are  dissolved 
in  water  with  addition  of  caustic  soda,  the  solution  shaken  with  ether  and 
the  aqueous  liquid  treated  with  excess  of  sodium  chloride  to  precipitate 
the  whole  of  the  soap.  The  liquid  is  then  filtered  and  the  insoluble  residue 
washed  with  saturated  sodium  chloride  solution,  the  liquid  being  then 
acidified  with  dilute  sulphuric  acid  and  the  phenol  estimated  by  means  of 
bromine  (see  Carbolic  Acid,  p.  330). 

(/)  MINERAL  AND  RESIN  OILS,  PARAFFIN  WAX,  TURPENTINE,  ETC. 
These  may  be  detected  by  extraction  of  the  soap  with  ether.  In  most 
cases,  mixtures  of  soap  with  mineral  or  resin  oils,  vaseline  and  the  like, 
constitute  lubricants  or  cart-grease,  analysis  of  which  is  dealt  with  in  the 
article  on  Lubricants  (see  p.  365). 


GLYCERINE 

Crude  glycerine  (saponification,  soap-lye  or  distillation  glycerine)  forms  a 
yellowish  or  brown  liquid  with  a  repellent  odour  and  an  acrid  taste,  while 
purified  glycerine  (refined,  distilled  or  double  distilled,  for  dynamite)  consists 
of  a  colourless  or  almost  colourless,  odourless,  syrupy  liquid  with  a  sweet 
taste. 

Analysis  of  commercial  glycerines  includes  qualitative  tests  to  ascertain 


464  GLYCERINE 

the  purity,  and  various  quantitative  determinations  to  decide  its  commercial 
•value  or  its  fitness  for  definite  purposes. 

A.     Crude  Glycerine 

Glycerine  liquors  from  soap-works,  either  as  they  are  or  after  concen- 
tration (as  usually  sold)  are  highly  contaminated  with  various  mineral 
salts  (chlorides,  sulphates,  sulphides,  sulphites,  thiosulphates,  lime,  alkali) 
and  organic  substances  (soaps,  tarry  substances,  proteins,  etc.).  Their 
analysis  is  usually  restricted  to  determinations  of  the  alkali  (free  and  com- 
bined), free  acid,  residue  on  evaporation,  water  and  glycerine.1 

Sampling. — The  sample  should  contain  portions  from  every  vessel 
forming  the  parcel  and  should  be  taken,  if  possible,  as  soon  as  these  are 
filled,  since  crude  glycerine  often  contains  suspended  matters  which  are 
gradually  deposited. 

If  such  deposition  has  already  occurred,  a  good  average  sample  may 
be  obtained  with  the  help  of  a  special  sampler.2 

Note  is  made  of  any  suspended  matter  observed  while  the  sample  is 
being  taken,  and  also  of  the  temperature  and  of  the  form  and  capacity  of 
the  vessels  when  these  are  not  similar. 

1.  Ash  and  Total  Alkali. — From  2  to  5  grams  of  the  glycerine  are 
weighed  in  a  platinum  dish  and  evaporated  carefully  over  a  direct  flame 
and  the  residue  charred  at  the  lowest  possible  temperature. 

The  carbonaceous  mass  is  then  extracted  with  boiling  water,  filtered 
and  washed.  The  filter  and  the  contained  charred  mass  are  incinerated 
in  the  same  dish,  the  aqueous  extract  and  wash-waters  being  added  and 
the  whole  evaporated  to  dryness  on  a  water-bath  and  again  ignited  carefully 
so  that  the  ash  does  not  fuse. 

The  ash  thus  obtained  is  weighed  and  then  dissolved  in  water  and  titrated 
with  normal  acid  (indicator  :  methyl  orange),  the  alkalinity  being  expressed 
as  percentage  of  Na2O  in  the  glycerine. 

2.  Free  Caustic  Alkali. — 20  grams  of  the  glycerine  are  weighed  in 
a  100  c.c.  flask,  dissolved  in  50  c.c.  of  recently  boiled  water,  treated  with 
excess  of  barium  chloride  solution  and  i  c.c.  of  alcoholic  phenolphthalein 
solution,  made  up  to  volume  with  boiled  water,  shaken  vigorously  and  left 
at  rest.     Subsequently  50  c.c.  of  the  clear  liquid  are  pipetted  off  and  titrated 
with  normal  acid.     The  free  alkali  is  calculated  as  Na2O  per  TOO  parts  of 
glycerine. 

3.  Alkali  as  Carbonate. — 10  grams  of  the  sample  are  diluted  with 
50  c.c.  of  distilled  water,  treated  with  sufficient  normal  acid  to  neutralise 
the  total  alkali  (see  i)  and  boiled  in  a  reflux  apparatus  for  15-20  minutes. 
The  condensei  is  washed  down  with  recently  boiled  distilled  water  and  the 
free  acid  titrated  with  normal  soda  in  presence  of  phenolphthalein. 

The  result  is  calculated  as  percentage  of  Na2O  and  from  this  is  deducted 

1  The  methods  were  fixed  in  1911  by  an  International  Commission  of  American, 
English,  German  and  French  analysts,  as  a  result  of  the  Congress  of  Glycerine  manu- 
facturers held  in  London  in  1909. 

2  Described  inZeitschr.  angew.  chem.,  191 1,  I,  p.  865,  and  L'Industria  chimica,  191 1, 
P-  245- 


GLYCERINE  465 

the  free  caustic  alkali  (see  2),  the  remainder  being  the  percentage  of  Na2O 
as  carbonate. 

4.  Alkali  combined  with  Organic  Acids. — The  percentage  of  Na2O 
existing  as  organic  salts  is  calculated  by  subtracting  from  the  total  Na20 
(i)  the  sum  of  the  free  Na2O  (2)  and  the  carbonated  Na20  (3). 

5.  Acidity. — Ten  grams  of  the  sample,  dissolved  in  50  c.c.  of  recently 
boiled  water,  are  titrated  with  normal  caustic  soda  in  presence  of  phenolph- 
thalein.     The  result  is  expressed  as  Na2O  necessary  to  neutralise  the  acidity 
of  100  grams  of  the  glycerine. 

6.  Residue  at  160°. — In  a  100  c.c.  measuring  flask,  10  grams  of  the 
glycerine  are  weighed,  diluted  with  a  little  water  and  treated  with  normal 
acid  or  alkali  (according  as  the  sample  is  alkaline  or  acid)  in  such  amount 
that  the  glycerine  assumes  an  alkalinity  corresponding  with  0-2%  of  Na2O. 
The  liquid  is  then  made  up  to  volume  and  shaken,  10  c.c.  (or,  if  the  sample 
is  very  impure,  a  lesser  quantity  sufficient  to  give  a  residue  not  exceeding 
30-40  milligrams)  being  transferred  to  a  tared  porcelain  dish  12  mm.  deep 
and  with  a  flat  base  6  cm.  in  diameter.     The  bulk  of  the  water  is  evaporated 
off  on  the  water-bath  and  the  dish  then  placed  in  an  air-oven  (30  X  30  X  30 
cm.),  which  is  furnished  with  a  thermometer,  rests  on  an  iron  plate  20  mm. 
thick,  and  has  half-way  up  a  shelf  covered  with  asbestos  board  on  which 
the  capsule  containing  the  glycerine  rests.     The  latter  is  heated  at  160° 
until  only  traces  of  thin  vapour  are  emitted,  then  removed  from  the  oven, 
allowed  to  cool,  0-5-1  c.c.  of  water  added  and  the  contents  gently  mixed. 
The  liquid  is  again  evaporated  on  the  water-bath  and  subsequently  on  the 
oven  at  160°  until  the  residue,  placed  within  the  oven,  no  longer  froths. 
This  operation  usually  requires  2-3  hours. 

At  this  point  the  dish  is  kept  in  the  oven  at  160°  for  exactly  one  hour, 
and  is  then  removed,  allowed  to  cool  in  a  desiccator  over  sulphuric  acid 
and  weighed.  The  residue  is  next  treated  with  water,  re-evaporated,  dried, 
kept  at  160°  for  an  hour  as  before,  this  procedure  being  repeated  until  the 
loss  occasioned  does  not  exceed  1-1-5  mgrms.  per  hour. 

The  weight  of  the  residue  at  160°  is  corrected  for  the  acid  or  alkali  added 
to  bring  the  alkalinity  to  the  desired  point.  With  acid  glycerine,  0-022 
gram  is  subtracted  for  each  c.c.  of  normal  alkali  added.  With  alkaline 
glycerine,  the  correction  applied  is  that  resulting  from  the  transformation 
of  NaOH  and  Na2C03  into  NaCl.  The  corrected  weight  gives  the  residue 
at  160°  and  is  calculated  for  100  grams  of  the  glycerine. 

The  residue  is  kept  for  the  determination  of  any  impurities  capable  of 
acetylation. 

7.  Organic  Residue. — The^organic  residue  represents  the  difference 
between  the  residue  at  160°  and  the  ash. 

It  should,  however,  be  noted  that  the  CO2  formed  for  the  transformation 
of  organic  acids  during  the  incineration  is  not  contained  in  the  organic 
residue. 

8.  Water. — On  a  clock-glass  of  about  15  c.c.  capacity  are  placed  2-3 
grams  of  very  voluminous  asbestos,  previously  well  washed  with  acid  and 
then  with  water  and  dried  at  100°.     The  whole  is  then  left  in  a  vacuum 
desiccator  over  sulphuric  acid  at  a  pressure~of  1-2  mm.  of  mercury  until 

A.C.  30 


466  GLYCERINE 

of  constant  weight.  From  i  to  1-5  gram  of  the  glycerine  is  then  dropped 
OB  to  the  asbestos  so  that  it  is  uniformly  distributed  ;  after  being  weighed 
again,  the  glass  is  left  in  the  desiccator  at  the  above  pressure  until  the 
weight  is  constant  (usually  about  48  hours  at  15°  are  required).  The  loss 
of  weight  represents  water. 

9.  Glycerine. — Either  of  two  methods  may  be  used1: 
A.  ACETYLATION  METHOD,  applicable  to  crude  glycerine,  provided  it 
contains  not  more  than  50%  of  water. 
Reagents  required : 

(a)  Acetic  anhydride  (puriss.),  which  should  be  carefully  examined  as 
to  purity  and  which  in  a  blank  esterification  experiment  should  not  require 
more  than  0-1-0-2  c.c.  of  normal  soda,  and  which  should  turn  only  slightly 
brown  when  boiled  for  an  hour  with  sodium  acetate. 

(b)  Pure  dry  sodium  acetate,  obtained  by  fusing  the  salt  in  a  platinum 
dish,  powdering  it  rapidly  and  storing  in  a  closed  vessel  in  a  desiccator. 
It  should  be  absolutely  free  from  moisture. 

(c)  Normal  caustic  soda  solution,  which  should  be  very  carefully  pre- 
pared with  well-boiled  water  and  should  be  quite  free  from  carbonate. 

(d)  Normal  sulphuric  acid. 

(e)  Phenolphthalein  solution,  containing  0-5  part  in  100  parts  of  alcohol 
and  neutralised. 

Procedure.  In  a  round-bottomed  flask  of  about  120  c.c.  capacity,  well 
washed  and  dried,  1-25-1-50  gram  of  the  glycerine  is  rapidly  weighed,  3 
grams  of  the  sodium  acetate  and  7-5  c.c.  of  acetic  anhydride  being  added. 
The  flask  is  then  connected  with  a  small  reflux  condenser  by  means  of  a 
ground  joint  or  a  rubber  stopper  (the  latter  should  be  first  purified  by 
exposure  to  the  vapour  of  boiling  acetic  anhydride)  and  the  liquid  boiled 
gently  for  about  an  hour.  It  is  then  cooled  somewhat  and  50  c.c.  of  recently 
boiled  hot  water  (at  about  80°)  added  by  way  of  the  condenser  tube,  the 
liquid  being  shaken  and  heated,  if  necessary — but  not  above  80° — until 
solution  is  complete  (excepting  for  a  few  black  flocks  due  to  impurities). 
The  condenser  tube  is  washed  down  with  a  little  boiled  water,  the  flask 
detached  and  the  stopper  or  ground  joint  also  washed  down.  The  liquid  is 
filtered  into  a  flask  holding  about  a  litre,  the  original  flask  and  filter  being 
thoroughly  washed  with  boiled,  cold  water.  2  c.c.  of  phenolphthalein 
solution  are  next  added  and  the  liquid  neutralised  with  the  normal  caustic 
soda  solution  (to  a  faint  yellowish-red  coloration),  care  being  taken  to 
shake  the  flask  continually  while  the  alkaline  solution  is  run  in  from  a 
burette. 

After  the  neutral  point  is  reached,  a  further  quantity  of  50  c.c.  of  normal 
caustic  soda  is  added,  the  flask  being  then  closed  with  a  stopper  traversed 
by  a  long  glass  tube  to  act  as  reflux  condenser,  and  the  liquid  boiled  gently 
for  15  minutes,  then  cooled  rapidly  and  the  excess  of  alkali  titrated  with 
the  normal  acid  until  the  original  yellowish-red  tint  reappears. 

At  the  same  time  a  check  experiment  is  made  under  the  same  conditions. 

From  the  quantity  of  caustic  soda  used  to  saponify  the  triacetin  (differ- 
ence between  the  volume  of  caustic  soda  added  after  neutralisation  and  the 
1  Recommended  by  the  Committee  mentioned  above. 


GLYCERINE  467 

volume  oi  acid  required  in  the  final  titration),  less  any  volume  found  in 
the  check  determination,  the  glycerine  is  calculated  :  i  c.c.  normal  alkali= 
0-03069  gram  of  glycerine. 

With  crude  soap-lye  glycerine,  when  this  contains  more  than  2-5%  of 
organic  residue  at  160°  (see  7),  the  residue  at  160°  obtained  as  in  6  (above) 
must  also  be  acetylated  in  the  manner  just  described  ;  if  the  result  thus 
obtained  corresponds  with  more  than  0-5%  of  glycerine  (on  the  residue 
itself),  the  excess  over  0-5%  is  deducted  from  the  percentage  of  glycerine 
found  in  the  sample  itself. 

For  distilled  saponification  glycerine  and  the  like,  acetylation  of  the 
organic  residue  is  carried  out  when  this  exceeds  i%,  the  procedure  being 
as  before  and  account  being  taken  only  of  the  excess  of  glycerine  over  0-5%. 

B.  DICHROMATE  METHOD.     Reagents  required  : 

(a)  Potassium  dichromate   (puriss.),   powdered,   dried  at   110-120°  and 
kept  in  a  well-closed  vessel. 

(b)  Standard  dichromate  solution  :    7-4564  grams  of  dichromate  (a)  are 
dissolved  in  water  to  i  litre. 

(c)  Ferrous  ammonium  sulphate,  to  be  titrated  with  the  dichromate 
as  follows  :  3-7282  grams  of  the  dichromate  are  dissolved  in  50  c.c.  of  water 
and  50  c.c.  of  dilute  sulphuric  acid  (g).     A  convenient  excess  of  ferrous 
ammonium  sulphate  (e.g.,  3-4  grams),  accurately  weighed,  is  then  added 
and  the  excess  determined  by  means  of  the  dichromate  solution  (b),  a  drop 
of  the  liquid  being  removed  from  time  to  time  and  tested  with  potassium 
fcrricyanide.     The  amount  of  dichromate  corresponding  with  i  gram  of 
pure  ferrous  ammonium  sulphate  is  then  calculated  (with  pure  products 
i  gram  of  the  sulphate  =  1-25  gram  of  the  dichromate). 

(d)  Silver  carbonate,  to  be  prepared  afresh  for  each  operation  by  treating 
140  c.c.  of  0-5%  silver  sulphate  solution  with  4-9  c.c.  of  normal  sodium 
carbonate  solution,  allowing  the  precipitate  to  deposit,  decanting  off  the 
liquid  and  washing  once  by  decantation. 

(e)  Basic  lead  acetate,  obtained  by  boiling  10%  neutral  lead  acetate 
solution  with  excess  of  litharge  for  an  hour  and  filtering  while  hot. 

(f)  Potassium  ferricyanide  in  0-1%  solution. 

(g)  Dilute  sulphuric  acid,  cone,  acid  being  mixed  with  its  own  volume 
of  water. 

Procedure.  20  grams  of  the  sample  are  made  up  to  250  c.c.  with 
water  in  a  250  c.c.  flask.  Of  this  solution,  25  c.c.  are  treated,  in  a  100  c.c. 
flask,  with  the  silver  carbonate  (d)  and,  after  about  10  minutes,  with  5  c.c. 
of  the  lead  acetate  (e),  the  liquid  being  then  made  up  to  the  mark  and  1-5 
c.c.  of  extra  water  added  to  compensate  for  the  volume  of  the  precipitate. 
The  whole  is  then  shaken  vigorously  and  filtered  through  a  dry  filter,  the 
first  10  c.c.  of  filtrate  being  discarded  and  the  remainder  refiltered  if  turbid.1 
A  small  portion  is  tested  to  ascertain  if  fresh  addition  of  the  lead  acetate 
gives  a  further  precipitate  :  if  this  is  the  case,  the  above  treatment  is  repeated 
with  a  fresh  volume  of  25  c.c.  of  the  original  solution  but  with  6  c.c.  of  the 
lead  acetate  ;  this  is,  however,  seldom  required. 

1  To  obtain  a  clear  filtrate,  a  few  c.c.  of  10%  sodium  sulphate  solution  may  be 
added  before  the  liquid  is  made  up  to  volume. 

A.C,  30* 


468  GLYCERINE 

25  c.c.  of  the  filtrate  are  treated  in  a  clean  beaker  (washed  with 
dichromate  and  sulphuric  acid)  with  12  drops  of  dilute  sulphuric  acid 
(i  :  4)  to  precipitate  the  excess  of  lead  and  then  with  37282  grams  of  the 
powdered  dichromate  (a)  and  25  c.c.  of  water.  When  the  dichromate  is 
dissolved,  50  c.c.  of  the  dilute  sulphuric  acid  (g)  are  added  and  the  beaker 
kept  in  a  boiling  water-bath  for  two  hours,  care  being  taken  to  protect  it 
from  organic  vapours  (alcohol,  etc.)  and  from  dust.  It  is  then  allowed  to 
cool,  an  exactly  weighed  amount  (in  excess)  of  ferrous  ammonium  sulphate 
(e-g-»  3~4  grams)  being  added  and  the  extent  of  the  excess  measured  by 
titration  with  the  dichromate  solution  (b),  potassium  ferrocyanide  being 
used,  as  before,  as  indicator. 

As  it  is  known  from  the  titration  of  the  ferrous  ammonium  sulphate 
(see  c)  with  how  much  dichromate  i  gram  of  the  ferrous  salt  corresponds, 
the  quantity  of  dichromate  used  in  oxidising  the  glycerine,  and  from  this 
the  amount  of  the  glycerine,  may  be  calculated  :  i  gram  of  the  dichromate 
—  0-13411  gram  of  glycerine. 

As  regards  these  two  methods,  adopted  by  the  International  Commission, 
Tortelli  and  Ceccherelli  1  point  out  that  only  the  second — the  dichromate  method 
— is  really  exact.  The  acetin  method,  according  to  the  accurate  investigations 
of  these  authors,  gives  inconstant  and  low  results. 

The  same  authors  also  suggest  some  practical  modifications  in  the  dichromate 
method. 

B.  Pure  Glycerine 

With  pure  glycerines  the  specific  gravity  is  determined  and  various 
common  impurities  (heavy  metals,  sulphates,  chlorides,  oxalates,  lime, 
arsenic,  acrolein,  formic  acid,  fats)  and  adulterations  (sugar,  dextrin) 
tested  for.  In  some  cases  the  chlorides  are  determined  and  possibly  the 
residue  at  160°  and  other  determinations  described  for  crude  glycerine. 
With  dynamite  glycerine,  a  nitration  test  is  made. 

1.  Specific  Gravity. — -This  is  determined  by  the  Westphal  balance, 
picnometer  or  hydrometer. 

If  the  glycerine  is  pure,  the  content  of  water  may  be  calculated  from 
the  specific  gravity  by  means  of  the  following  table  (page  469). 

2.  Detection   of   Impurities   and    Adulterations. — This  is   effected 
by  means  of  the  following  tests  : 

(a)  i  volume  of  the  glycerine  is  dissolved  in  5  vols.  of  water  and  the 
reaction  of  the  solution  tested  with  litmus  paper  :    pure  glycerine  should 
be  neutral. 

Aliquot  parts  of  the  same  solution  are  then  treated  with  hydrogen 
sulphide  and  with  ammonium  sulphide  to  ascertain  if  heavy  metals  are 
present  (blown  coloration)  ;  with  barium  chloride  for  the  detection  of 
sulphates,  with  silvei  nitrate  for  that  of  chlorides,  with  calcium  chloride  for 
that  of  oxalates  and  with  ammonium  oxalate  for  that  of  calcium  salts. 

(b)  i  c.c.  of  the  glycerine  is  treated  with  5  c.c.  of  Bettendorf's  reagent 
for  the  detection  of  arsenic  :   no  coloration  should  be  detectable  within  an 
hour. 

1  Annali  di  chimica  applicata,   1914,   I,  p.  514. 


GLYCERINE 


469 


TABLES    LI 
Specific  Gravity  of  Aqueous  Glycerine 


Specific  gravity  according  to 


Specific  gravity  according  to 


rercentage 

1'ercentage 

l.t-nz  at  12-14° 
Water  at  12°=  I 

Gerlach  at  15° 
Water  at  1  5°=  i 

by  weight 
of 
Glycerine. 

Lenz  at  12-14° 
Water  at  12°=  i 

Gerlach  at  15° 
.Vaterat  15"=! 

bv  weight 
of 
Glycerine. 

1-2691 

1-2653 

TOO 

I-22I2 

1-2184 

82 

1-2664 

1-2628 

99 

1-2185 

1-2157 

81 

1-2637 

1-2602 

98 

1-2159 

1-2130 

80 

1-2610 

1-2577 

97 

1-2016 

1-1990 

75 

1-2584 

I-2552 

96 

1-1889 

1-1850 

70 

1-2557 

1-2526 

95 

1-1733 

1-1711 

65 

I-253I 

1-2501 

94 

1-1582 

1-1570 

60 

1-2504 

1-2476 

93 

1-1455 

1-1430 

55 

1-2478 

1-2451 

92 

1-1320 

1-1290 

50 

1-2451 

1-2425 

9i 

1-1183 

I-H55 

45 

1-2425 

1-2400 

90 

1-1045 

I-I02O 

40 

1-2398 

1-2373 

89 

1-0907 

1-0885 

35 

1-2372 

1-2346 

88 

1-0771 

I-0750 

30 

1-2345 

I-23I9 

87 

.1-0635 

I-O62O 

25 

1-2318 

1-2292 

86 

1-0498 

1-0490 

20 

1-2292 

1-2265 

85 

1-0374 



15 

1-2265 

1-2238 

84 

1-0245 

1-0245 

10 

1-2238 

I-22II 

83 

1-0123 

5 

(c)  i  c.c.  of  the  glycerine  and  i  c.c.   of  ammonia  are  heated  to  60° 
and  3  drops  of  silver  nitrate  solution  then  added  :    the  appearance  of  a 
brown  coloration  or  deposit  within  5  minutes  denotes  the  presence  of  acrolein 
or  formic  acid. 

(d)  i  c.c.  is  heated  with  i  c.c.  of  15%  sodium  hydroxide  solution  : 
evolution  of  ammonia  indicates  the  presence  of  ammonium  salts,  or  yellowing 
of  the  solution  the  presence  of  glucose.     The  presence  of  the  latter  may  be 
confirmed  by  boiling  a  few  drops  of  the  glycerine  with  Fehling's  solution 
(red  precipitate). 

(e)  i  c.c.  is  heated  gently  with  dilute  sulphuric  acid  to  ascertain  if 
an  unpleasant  rancid  odour  is  evolved  (fatty  substances)  ;  the  liquid  is  then 
neutralised  and  boiled  with  Fehling's  solution  (sugar). 

(/)  i  volume  of  the  glycerine  is  treated  with  about  2  vols.  of  strong 
alcohol :  turbidity  denotes  presence  of  gum  or  dextrin. 

(g)  A  few  c.c.  of  the  glycerine  are  evaporated  in  a  small  dish  to  ascer- 
tain if  any  residue  remains  (usually  mineral  substances). 

3.  Chlorides. — A  known  weight  of  the  glycerine  is  carefully  burnt,  the 
residue  charred  at  a  low  temperature  and  lixiviated  with  water  and  the 
chlorine  in  the  solution  determined  volumetrically.     The  result  is  expressed 
as  sodium  chloride. 

4.  Nitration  Test  (for  dynamite  glycerine). —  Into  a  very  wide  beaker, 
150  grams  of  nitrating  mixture  (i  part  by  weight  of  nitric  acid  of  D  =  1-5 


4^0  GLYCERINE 

and  2  parts  by  weight  of  sulphuric  acid  of  D  —  1-845)  are  poured  and  on 
to  this  are  carefully  dropped  20  grams  of  the  glycerine,  the  beaker  being 
externally  cooled  with  water  meanwhile.  The  product  is  subsequently 
transferred,  with  every  precaution,  to  a  graduated  cylinder  and  note  taken 
if  the  nitroglycerine  separates  promptly  and  if  it  is  pale  and  clear.  When 
the  separation  of  the  nitroglycerine  from  the  acid  liquid  is  sharp,  the  volume 
of  the  former  is  measured  ;  multiplication  of  this  volume  by  1-609  (specific 
gravity  of  nitroglycerine  at  15°)  gives  the  weight. 

*** 

Glycerine  liquors  obtained  directly  by  saponification  with  alkali  or  in  an 
autoclave  contain  5-10%  of  glycerine,  whereas  those  resulting  from  saponifica- 
tion by  Twitchell's  method  or  by  enzymes  contain  12-19%. 

Crude  glycerine  (concentrated)  usually  contains  80-90%  of  glycerine  and 
varying  quantities  of  salts  (ash),  residue  fixed  at  160°,  free  acids  or  alkalies,  etc. 

Refined  glycerine  (pure,  puriss.)  should  be  free  or  almost  so  from  the  different 
impurities  already  mentioned  (see  Pure  Glycerine,  2). 

Double  distilled  glycerine  for  pharmaceutical  purposes  should,  in  particular, 
satisfy  the  various  tests  indicated  under  2. 

Dynamite  glycerine  should  have  a  specific  gravity  not  less  than  1-261,  should 
be  perfectly  neutral,  should  contain  no  more  than  traces  of  chlorides  (not  more 
than  0-025%  °f  NaCl),  sulphates,  lime,  magnesia,  alumina  and  reducing  sub- 
stances, and  not  more  than  0-25%  of  residue  fixed  at  160°.  In  the  nitration 
test  it  should  give  not  less  than  200  %  of  nitroglycerine  (theoretical  yield,  246-7%), 
which  should  separate  promptly  as  a  colourless  or  almost  colourless,  perfectly 
clear  liquid. 


INDEX 


Abel-Pensky  apparatus,  344 
Acetargol,  25 
Acetic  acid,  18 
Acetone,  16 

—  oils,  17 
Acetyl  number,  378 

—  acid  value,  378 

-  saponifi cation  number,  378 
Acetylene,  58 

Acid  number,  374 
Alcohol,  38 
Alfenide,  268 
Alluman,  272 
Alum,  42 
Aluminium,  271,  272 

—  acetate,  42 

bronze,  271,  276 

—  copper  alloys,  276 

-  magnesium  alloys,  276 

-  manganese,  271 

—  nickel,  271 

plating,  294 

sulphate,  43 

Ammonia,  45 
Ammonium  carbonate,  46 

—  chloride,  46 

—  citrate  solution,  123 

molybdate  solution,  132 

-  persulphate,  47 

—  sulphate,  125 

—  sulphocyanide,  47 

-  thiocyanate,  47 

-  vanadate,  48 
Amyl  acetate,  48 

—  alcohol,  38 
Aniline,  50 

—  oils,  51 
Anthiacene,  328 

—  oils,  320 

Antifriction  metals,  265 
Antimonin,  53 
Antimony,  250 

—  and  potassium  tartrate,  52 
Apatites,  128 

Appiani's  method  for  determining  phos- 
phoric acid,  130 
Arachidic  acid,  395 
Arachis  oil,  395 
Astatki,  360 

Barbouze's  alloy,  271 
Barium  chloride,  53 

-  hydroxide,  54 

-  peroxide,  53 


Baryta,  54 
Beeswax,  434 
Bellier's  reaction,  394 
Benzene,  323 
Benzine,  340 
Benzoles,  323 
Bergwachs,  365 
Bettendorf 's  reagent,  1 8 
Bieber's  reaction,  405 
Blankite,  69 
Bleaching  powder,  55 
Bomb,  Calorimetric,  303 
Bone  ash,  128 
—  black,  128 

—  meal,  128 
Bones,  128 
Boracite,  56 
Borates,  Natural,  56 
Borax,  56 

Boric  acid,  19 

Borocalcite,  56 

Boronatrocalcite,  56 

Boutron  and  Boudet's  method,  2 

Brasses,  Complex,  229 

— ,  Ordinary,  224 

— ,  Special,  227 
Brass-plating,  294 
Braunite,  74 
Briquettes,  315 
Bromine,  56 
Bronzes,  Ordinary,  232 

,  Special,  236 

Brulle's  reaction,  394 
Burnstyn  degrees,  375 

Cacao  butter,  4 1 3 
Calcium  acetate,  57 

—  carbide,  58 

—  citrate,  59 

—  cyanamide,  128 

—  nitrate,  128 
-  oxide,  151 

Calomel,  77 
Calorific  power,  300 
Calorimeter,  Hempel,  307 

,  Lewis  Thompson,  30 1 

— ,  Mahler  bomb,  303 
Calorimetric  bomb,  303,  307 
Candelite,  446 
Candles,  456 
Carbolic  acid,  330 
Carbon  disulphide,  (>> 

tetrachloride,  62 

Carbonic  acid,  20 


471 


472 


INDEX 


Carnallite,  134 

Carnot's  reagent,  119 

Cart-grease,  365 

Caustic  potash,  86 
—  soda,  10 1 

Cement  materials,  138 

Cements,  152 

— ,  Composition  of,  158 

— ,  -  -  quick-setting,  159 

— ,  —          —  slow-setting,  160 


— ,  Grappier's,  152,  157 
— ,  Mixed,  152,  157 
— ,  Natural,  152,  156 
— ,  Portland,  152,  156 
— ,  Roman,  152 
— ,  Sand,  157 
— ,  Slag,  152,  157 

Ceresine,  363,  389 

Chalcopyrite,  114 

Charcoal,  308 

Chili  saltpetre,  126 

Chinese  tallow,  4 1 7 

Chloride  of  lime,  63 

Chloroform,  63 

Cholesterol,  388 

Chrome  alum,  77 

Chromic  acid,  2 1 

Chromium  acetate,  77 

chloride,  77 

fluoride,  77 

formate,  77 

hydroxide,  77 

—  nitroacetate,  77 

—  sulphate,  77 

—  sulphoacetate,  77 
Citric  acid,  2 1 

—  solution,  132 
Citrometer,  23 

Clark's  hardness  table,  4 
Clays,  144 
Coal,  297,  309 

tar,  317 

Coke,  315 

Colorimeter,  Stammer's,  343 
Congo  red  paper,  333 
Copper,  214 

—  aluminium  alloys,  276 

plating,  294 

silicide,  221 

—  silver-gold  alloys,  290 

—  sulphate,  63 
Coprolites,  128 
Corleir  method,  164 
Corrosive  sublimate,  76 
Coryphol,  446 

Cream  of  tartar,  80 
Cupellation  of  gold,  286 

—  silver,  278 
Cupro-manganese,  222 

—  silicon,  221 

Dalican's  table,  420 
Decroline,  69 
Degragene,  454 


Degras,  454 
Dobbin's  reagent,  96 
Duralumin,  272 

Eau  de  Javelle,  56 

-  Labarraque,  56 
Eggertz  tube,  170 
Elaidin  test,  394 
Electro-analysis  of  metals,  209 
Ester  number,  376 
Ether,  65 
Evaporative  power  of  fuel,  300 

Facchini  and  Dorta's  method,  398 
Fat,  Bone,  426 

,  Hog's,  421 

,  Mahwa,  417 

— ,  Mowrah,  417 

— ,  Stillingia,  417 

— ,  Wool,  439 
Fats,  370 

,  Animal,  418 

,  Vegetable,  413,  414 

Ferric  chloride,  65 
—  nitrate,  78 

sulphate,  78 

Ferro-aluminium,  208 

chrome,  202 


manganese,  197 
molybdenum,  206 
silicon,  195 
titanium,  207 
tungsten,  204 
vanadium,  205 


Ferrous  acetate,  66 

—  sulphate,  66 
Ferrugine,  78 
Fertilisers,  117 

,  Complex,  136 

,  Nitrogenous,  125 

— ,  Phosphatic,  128 

— ,  Potash,  134 
Flowers  of  sulphur,  1 10 
Formaldehyde,  67 
Formic  acid,  25 
Fortini  test,  399 
Fuels,  297 

,  Agglomerated,  315 

Fusel  oil,  38 

Gay-Lussac's     method     of     determining 

silver,  281 
German  silver,  268 
Gilding,  292 
Glycerine,  463 

,  Crude,  464 

— ,  Pure,  468 
Gold,  286 

copper  alloys,  286 

plating,  292 

silver-copper  alloys,  290 

Griess's  reagent,  6 

Guano,  136,  137 
Gypsum,  157 


INDEX 


473 


Halphen's  bromine  reagent,  404 

reaction,  402 

Hard  salt,  134 
Hardness  of  water,  2,  15 
Hauchecorne's  reaction,  393 
Hausmannite,  74 
Hehner  number,  382 
Heydenreich's  reaction,  393 
Hiibl's  iodine  number,  379 
Hydraulic  index,  1 52 

-  limes,  152,  158 

—  modulus,  152 
Hydrochloric  acid,  26 
Hydrofluoric  acid,  27 
Hydrofluosilicic  acid,  28 
Hydrogen  peroxide,  68 
Hydrosulphites,  69 
Hydroxy-acids  in  fats,  383 
Hyraldite,  69 

Imitation  plate,  271 
Impregnating  oils,  322 
Inquartation,  286 
Iodine,  70 

—  number,  379 
Iron,  162 
,  Arsenic  in,  179 

— ,  Carbon  in,  169 

— ,  Combined  carbon  in,  169 

— ,  Graphitic  carbon  in,  169 

• — ,  Manganese  in,  1 72 

— ,  Phosphorus  in,  1 73 

— ,  Silicon  in,  171 

— ,  Sulphur  in,  176 
Isoamyl  alcohol,  38 

Javelle,  Eau  de,  56 

Kainit,  134 
Kerosene,  343 
Kjeldahl  method,  122 
Kottstorfer  degrees,  375 

Labarraque,  Eau  de,  56 

Lactic  acid,  28 

Lactolin,  88 

Lactones  in  fats,  383 

Lanoline,  439 

Lard,  421 

Le  Chatelier's  volumenometer,  153 

Lead, 244 

— -  acetate,  71 

— ,  Hard,  247 

-  plating,  294 

-  tin  alloys,  258 
Lemon  juice,  23 
Lignite,  309,  310 
Lignoceric  acid,  395 
Lime,  151 

— ,  Chloride  of,  55 

— ,  Hydraulic,  152 
Limestones,  138 
Liver  of  sulphur,  9 1 
Lubricants,  Emulsive,  368 
,  Stiff,  365 


Magnaliurn,  271,  276 
Magnesia,  71 

—  mixture,  123 
Magnesium  aluminium  alloys,  276 

—  chloride,  73 

—  oxide,  71 

—  sulphate,  74 
Manganese  dioxide,  74 
Manganite,  74 
Marls,  138 

Maumen6  number,  391 
Mazut,  360 
Mercuric  chloride,  76 
Mercurous  chloride,  77 

Messinger's  method  of  estimating  acetone, 

40 
Methyl  alcohol,  38 

— ,  Density  of  aqueous,  40 
Michaelis  volumenometer,  1 5 1 
Milliau's  reaction,  401,  402 
Mineral  oils,  335 

—  oil  residues,  360 
Mirbane,  Essence  of,  79 
Montan  wax,  365 
Mordants,  Chrome,  77 
,  Iron,  78 

— ,  Tin,  109 
Mortar,  Normal,  148 

Naphthalene,  327 
Nessler's  solution,  6 
Nickel,  266 

—  plating,  293 
Nitre,  89 
Nitric  acid,  29 
Nitrobenzene,  79 
Nitrometer,  126 
Normal  mortar,  148 
-  sand,  155 

Oil,  Acetone,  17 

— ,  Almond,  405 

• — -,  Aniline,  51 

— ,  Anthracene,  320 

— ,  Arachis,  395 

— ,  Boiled  linseed,  443 

— ,  Castor,  408 

— ,  Coco-nut,  416 

— ,  Cod-liver,  431 

— ,  Colza,  398 

— ,  Cottonseed,  401 

— ,  Foot,  428 

— ,  Fusel,  38 

— ,  Gas,  349 
,  Heavy,  350 

— ,  Heavy  tar,  320 

,  Illip6-nut,  417 

,  Impregnating,  322 

,  Light  mineral,  340 

— ,  Light  tar,  319 

— ,  Lighting,  343 

— ,  Linseed,  403 

— ,  Lubricating,  350 

— ,  Mahwa,  417 


474 


INDEX 


Oil,  Middle,  349 

-,  Middle  tar,  320 

— ,  Mineral,  335 

,  Mowrah,  417 

,  Olive,  406 

— ,  Palm,  416 

• ,  Palm-kernel,  417 

,  Ravison,  401 

residues,  360 

,  Seal,  430 

,  Sesame,  412 

,  Shale,  335 

— ,  Spermaceti,  442 

— ,  Sulphocarbon,  407 

— ,  Turkey-red,  447 

— ,  Whale,  430 
Oils,  370 

— ,  Blown,  445 

— ,  Blubber  (train),  428,  430 

— ,  Hardened  or  hydrogenised,  446 

— ,  Liver,  428 
,  Marine  animal,  428,  432 

— ,  Oxidised,  445 
,  Terrestrial  animal,  429 

— ,  Vegetable,  395,  410 
Oleic  acid,  449 
Oleine,  449 

,  Wool  fat,  45 1 

Oleomargarine,  420 
Oleum,  34 
Ostatki,  360 
Oxalic  acid,  30 
Oxidised  metals,  295 
Ozokerite,  335 

Packfong,  268 
Pandermite,  56 
Paraffin  oil,  343 

wax,  362 

Parting,  286,  288 

Peat,  308 

Pensky-Martens  apparatus,  351 

Petroleum,  335 

Phenol,  330 

Phenol-sulphuric  acid,  123 
Phosphate,  Precipitated,  134 

— ,  Redonda,  133 

— ,  Wiborg,  133 
Phosphates,  128 
Phosphor-bronze,  236 

copper,  221 

tin,  257 

Phosphoric  acid,  31 
Phosphorites,  128 
Phosphosulphuric  acid,  122 
Photometry,  345 
Phytosterol,  389 
Picric  acid,  32 
Pitch,  321 

Plate,  Imitation,  271 
Potash  manure  salts,  1 35 
Potassium  hypochlorite,  56 

-  persulphate,  47 
salts,  79-91 


Potassium  silicate,  104 
Pozzolane,  146,  150 
Psilomelan,  74 
Pyridine,  332 
Pyrites,  114 
Pyroligneous  acid,  18 
Pyrolignite  of  iron,  66 

-  lead,  71 
Pyrolusite,  74 

Reaction,  Bellier's,  394 

— ,  Bieber's,  405 

— ,  Brulle's,  394 

— ,  Halphen's,  402 

— ,  Hauchecorne's,  393 
,  Heydenreich's,  393 

— ,  Landolt's,  330 
— — ,  Milliau's,  402 

,  Villa vecchia  and  Fabris',  412 

Redonda  phosphate,  133 

Reichert-Meissl  number,  377 

Riche  and   Halphen's  test  for  lamp-oils, 

348 
Rongalite,  69 

Saltpetre,  89 

— ,  Chili,  126 
Sand,  Normal,  155 
Santorin,  146 
Saponification,  373 

-  number,  375 
Scheibler's  apparatus,  141 

Schulze  and  Tiemann's  method  for  esti- 
mating nitrogen,  120 
Silico-spiegeleisen,  202 
Silicon  ferro-manganese,  202 
Silver,  277 

alloys,  277 

— — ,  German,  268 

—  gold-copper  alloys,  290 

-  nitrate,  92 

-  plating,  292 
Sitosterol,  389 
Slag,  Martin,  133 

— ,  Thomas,  132,  133 
Slags,  132,  146 
Soaps,  458 
Soda,  Ammonia,  98 

ash,  95 

— ,  Caustic,  10 1 

—  crystals,  95 
,  Leblanc,  98 

Sodium  arsenite,  Standard  solution  of,  55 
hydrosulphite,  69 

-  hypochlorite,  56 

nitrate,  126 

-  perborate,  56,  102 
salts,  92-108 

sulphoxylate,  70 

Sorrel,  Salts  of,  90 
Spermaceti,  441 

oil,  442 

Spiegeleisen,  197 
Stable  manure,  136 


INDEX 


475 


Stannic  chloride,  108 
Stannous  chloride,  1 10 
Starch-iodide  paper,  55 
Stassfurt  salts,  134 
Stearic  acid,  451 
Stearine,  451 

— ,  Wool  fat,  453 
Steels,  Chrome,  183 

,  Chrome-nickel,  193 

,  Chrome-tungsten,  193 

,  Chrome- vanadium,  194 

— • — ,  Compositions  of,  181 

• ,  Manganese,  187 

,  Molybdenum,  191 

— ,  Nickel,  1 86 

— ,  Silicon,  193 
,  Special,  182 

— ,  Tungsten,  188 
-,  Vanadium,  189 


Sulphoricinate,  Ammonium,  447 

- — ,  Sodium,  447 
Sulphur,  1 10 

— ,  Coppered,  112 

— -,  Crude,  112 
— - — ,  Liver  of,  91 
— — -  minerals,  1 1 1 

— ,  Precipitated,  113 

— ,  Refined,  112 
Sulphuric  acid,  33 

— ,  Fuming,  34 
Sulphurimeter,  112 
Superphosphates,  130 
Sylvine,  134 

Talgol,  446 
Tallow,  418 

- — ,  Chinese,  417 

— ,  Vegetable,  4 1 7 
Tar,  Coal,  317 

—  oils,  319,  320 
Tartar,  Cream  of,  80 

—  emetic,  52 
Tartaric  acid,  35 
Tartars,  36 

Tetmajer  rammer,  154 
Thermo-oleometer,  391 
Tin,  252 

--  compounds,  109 

foil,  260 

lead  alloys,  258 

-  phosphide,  257 
• — —  plate,  254 

-  plating,  294 
Toluidine,  52 


Tortelli  and  Fortini's  test  for  cruciferous 
oils,  399 

Tortelli  and  Ruggeri's  method  for  detect- 
ing arachidic  acid,  395 

Tortelli  and  Ruggeri's  separation  of  fatty 
acids,  384 

Tortelli  test,  399 

Touchstone,  286 

Trass,  146 

Twitchell's  method  for  estimating  resin, 
39° 

Vaseline,  360 
Vegetable  fats,  413,  414 

-  tallow,  417 

-  waxes,  413 
Vicat  needle,  155 

Villavecchia    and     Fabris'    reaction,    412 

Viscometers,  352 

Volatile  acid  number,  377 

Volhard's  method  for  estimating  chlorine, 

10 
Volhard's  method    for    estimating  silver. 

280 

Volumenometer,  Le  Chatelier's,  153 
— ,  Michaelis,  151 

Wagner's  method  for  estimating  phos- 
phoric acid,  132 

Water,  Composition  of  —  supplies,  1 3 
—  for  industrial  purposes,  12 

—  glass,  103 
— ,  Potable,  i 

Wax,  Bees,  434 

,  Montan,  365 

,  Paraffin,  362 

Waxes,  370,  433,  441 
— ,  Vegetable,  413 
White  metal,  260 
Wiborg  phosphates,  133 
Wijs's  iodine  number,  380 
Wine  lees,  36 
Wood  spirit,  42 
Wool  fat,  439 

—  oleine,  451 

—  stearine,  453 

-  wax,  453 

Zinc,  241 

—  dust,  243 

-  plating,  294 

-  sulphoxylate,  70 
Zisium,  272 

Ziskon,  271 


Printed  by  Butler  &  Tanner,  Frame  and  London. 


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